OpenGL drawing a Hexigon with vertices

OpenGL drawing a Hexigon with vertices - android

Im trying to make a basic shape ( Hexigon ) to start and learn some basics about OpenGL on the Android platform and i have a little problem.
I have successfully made a pointy Hexagon, but when i convert it into a flat Hexygon it doesnt render correctly. Here is some code, for you guys to figure out the problem ( probably a easy fix.. )
vertices / indices
//flat hexagon
private float verticesFlat[] = {
0.0f, 0.0f, 0.0f, //center
-0.5f, 1.0f, 0.0f, // left top
0.5f, 1.0f, 0.0f, // right top
1.0f, 0.0f, 0.0f, // right
0.5f, 1.0f, 0.0f, // right bottom
-0.5f, -1.0f, 0.0f, // left bottom
-1.0f, 0.0f, 0.0f, // left
};
private short[] indices = { 0, 1, 2, 3, 4, 5, 6, 1 };
standard vertex / index Buffers..
// a float is 4 bytes, therefore we multiply the number if
// vertices with 4.
ByteBuffer vbb = ByteBuffer.allocateDirect(verticesFlat.length * 4);
vbb.order(ByteOrder.nativeOrder());
vertexBuffer = vbb.asFloatBuffer();
vertexBuffer.put(verticesFlat);
vertexBuffer.position(0);
// short is 2 bytes, therefore we multiply the number if
// vertices with 2.
ByteBuffer ibb = ByteBuffer.allocateDirect(indices.length * 2);
ibb.order(ByteOrder.nativeOrder());
indexBuffer = ibb.asShortBuffer();
indexBuffer.put(indices);
indexBuffer.position(0);
The onDraw(GL10 gl):
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
GLU.gluLookAt(gl, 0, 0, -5, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glDrawElements(GL10.GL_TRIANGLE_FAN, indices.length, GL10.GL_UNSIGNED_SHORT, indexBuffer);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
The result im getting is illustrated in the image below:

Should be
private float verticesFlat[] = {
0.0f, 0.0f, 0.0f, //center
-0.5f, 1.0f, 0.0f, // left top
0.5f, 1.0f, 0.0f, // right top
1.0f, 0.0f, 0.0f, // right
0.5f, -1.0f, 0.0f, // right bottom (notice sign)
-0.5f, -1.0f, 0.0f, // left bottom
-1.0f, 0.0f, 0.0f, // left
};

Related

Android OpenGLES - Cube not showing on some devices

I recently used moho example to create a cube in android with OpenGLES 1.1 and I don't know why it works on some devices and not work on others with same Android version.
If someone can help me...
This is MyGLRenderer:
public class MyGLRenderer implements GLSurfaceView.Renderer {
Context context; // Application's context
private Cube cube;
private Triangle triangle;
private final float[] mRotationMatrix = new float[16];
// Constructor with global application context
public MyGLRenderer(Context context) {
this.context = context;
this.cube = new Cube();
this.triangle = new Triangle();
initRotationMatrix();
}
private void initRotationMatrix() {
mRotationMatrix[0] = 1;
mRotationMatrix[4] = 1;
mRotationMatrix[8] = 1;
mRotationMatrix[12] = 1;
}
// Call back when the surface is first created or re-created
#Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glClearColor(1.0f, 1.0f, 1.0f, 1.0f); // Set color's clear-value to black
gl.glClearDepthf(1.0f); // Set depth's clear-value to farthest
gl.glEnable(GL10.GL_DEPTH_TEST); // Enables depth-buffer for hidden surface removal
gl.glDepthFunc(GL10.GL_LEQUAL); // The type of depth testing to do
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); // nice perspective view
gl.glShadeModel(GL10.GL_SMOOTH); // Enable smooth shading of color
gl.glDisable(GL10.GL_DITHER); // Disable dithering for better performance
// You OpenGL|ES initialization code here
// ......
}
// Call back after onSurfaceCreated() or whenever the window's size changes
#Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
if (height == 0) height = 1; // To prevent divide by zero
float aspect = (float)width / height;
// Set the viewport (display area) to cover the entire window
gl.glViewport(0, 0, width, height);
// Setup perspective projection, with aspect ratio matches viewport
gl.glMatrixMode(GL10.GL_PROJECTION); // Select projection matrix
gl.glLoadIdentity(); // Reset projection matrix
// Use perspective projection
GLU.gluPerspective(gl, 45, aspect, 0.1f, 100.0f);
gl.glMatrixMode(GL10.GL_MODELVIEW); // Select model-view matrix
gl.glLoadIdentity(); // Reset
}
// Call back to draw the current frame.
#Override
public void onDrawFrame(GL10 gl) {
// Clear color and depth buffers using clear-value set earlier
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
// ----- Render the Color Cube -----
gl.glLoadIdentity(); // Reset the model-view matrix
gl.glTranslatef(cube.getPosX(), cube.getPosY(), cube.getPosZ()); // Translate
gl.glScalef(0.8f, 0.8f, 0.8f); // Scale down (NEW)
gl.glRotatef(cube.getAngleX(), 1.0f, 0.0f, 0.0f); // rotate about the axis (1, 1, 1) (NEW)
gl.glRotatef(cube.getAngleY(), 0.0f, 1.0f, 0.0f); // rotate about the axis (1, 1, 1) (NEW)
gl.glRotatef(cube.getAngleZ(), 0.0f, 0.0f, 1.0f); // rotate about the axis (1, 1, 1) (NEW)
gl.glMultMatrixf(mRotationMatrix, 0);
//cube.setAngleX(cube.getAngleX() - 1.5f);
//cube.setAngleY(cube.getAngleY() - 1.5f);
//cube.setAngleZ(cube.getAngleZ() - 1.5f);
// LIGHT
// float[] position = {0f, -5f, 0f, 1f};
// float[] ambient = {1f, 1f, 1f, 1f};
// float[] direction = {0f, 1f, 0f};
// gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_POSITION, position, 0);
// gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_AMBIENT, ambient, 0);
// gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_SPOT_DIRECTION, direction, 0);
// gl.glLightf(GL10.GL_LIGHT0, GL10.GL_SPOT_CUTOFF, 100.0f);
//
// gl.glEnable(GL10.GL_LIGHTING);
// gl.glEnable(GL10.GL_LIGHT0);
cube.draw(gl);
// triangle.draw(gl);
}
public Cube getCube() {
return cube;
}
public float[] getmRotationMatrix() {
return mRotationMatrix;
}
}
This is my Cube class:
public class Cube {
private FloatBuffer vertexBuffer; // Buffer for vertex-array
private int numFaces = 6;
private float posX = 0.0f, posY = 0.0f, posZ = -6.0f;
private float angleX = 0.0f, angleY = 0.0F, angleZ = 0.0f;
/*
private float[][] colors = { // Colors of the 6 faces
{1.0f, 0.5f, 0.0f, 1.0f}, // 0. orange
{1.0f, 0.0f, 1.0f, 1.0f}, // 1. purple
{0.0f, 1.0f, 0.0f, 1.0f}, // 2. green
{0.0f, 0.0f, 1.0f, 1.0f}, // 3. blue
{1.0f, 0.0f, 0.0f, 1.0f}, // 4. red
{1.0f, 1.0f, 0.0f, 1.0f} // 5. yellow
};
*/
private float[][] colors = { // Colors of the 6 faces
{0.0f, 1.0f, 0.0f, 1.0f}, // green
{0.0f, 1.0f, 0.0f, 1.0f}, // green
{0.0f, 1.0f, 0.0f, 1.0f}, // green
{0.0f, 1.0f, 0.0f, 1.0f}, // green
{0.0f, 1.0f, 0.0f, 1.0f}, // green
{0.0f, 1.0f, 0.0f, 1.0f} // green
};
private float[] vertices = { // Vertices of the 6 faces
// FRONT
-1.0f, -1.0f, 1.0f, // 0. left-bottom-front
1.0f, -1.0f, 1.0f, // 1. right-bottom-front
-1.0f, 1.0f, 1.0f, // 2. left-top-front
1.0f, 1.0f, 1.0f, // 3. right-top-front
// BACK
1.0f, -1.0f, -1.0f, // 6. right-bottom-back
-1.0f, -1.0f, -1.0f, // 4. left-bottom-back
1.0f, 1.0f, -1.0f, // 7. right-top-back
-1.0f, 1.0f, -1.0f, // 5. left-top-back
// LEFT
-1.0f, -1.0f, -1.0f, // 4. left-bottom-back
-1.0f, -1.0f, 1.0f, // 0. left-bottom-front
-1.0f, 1.0f, -1.0f, // 5. left-top-back
-1.0f, 1.0f, 1.0f, // 2. left-top-front
// RIGHT
1.0f, -1.0f, 1.0f, // 1. right-bottom-front
1.0f, -1.0f, -1.0f, // 6. right-bottom-back
1.0f, 1.0f, 1.0f, // 3. right-top-front
1.0f, 1.0f, -1.0f, // 7. right-top-back
// TOP
-1.0f, 1.0f, 1.0f, // 2. left-top-front
1.0f, 1.0f, 1.0f, // 3. right-top-front
-1.0f, 1.0f, -1.0f, // 5. left-top-back
1.0f, 1.0f, -1.0f, // 7. right-top-back
// BOTTOM
-1.0f, -1.0f, -1.0f, // 4. left-bottom-back
1.0f, -1.0f, -1.0f, // 6. right-bottom-back
-1.0f, -1.0f, 1.0f, // 0. left-bottom-front
1.0f, -1.0f, 1.0f // 1. right-bottom-front
};
// Constructor - Set up the buffers
public Cube() {
// Setup vertex-array buffer. Vertices in float. An float has 4 bytes
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
vbb.order(ByteOrder.nativeOrder()); // Use native byte order
vertexBuffer = vbb.asFloatBuffer(); // Convert from byte to float
vertexBuffer.put(vertices); // Copy data into buffer
vertexBuffer.position(0); // Rewind
}
// Draw the shape
public void draw(GL10 gl) {
gl.glFrontFace(GL10.GL_CCW); // Front face in counter-clockwise orientation
gl.glEnable(GL10.GL_CULL_FACE); // Enable cull face
gl.glCullFace(GL10.GL_BACK); // Cull the back face (don't display)
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
// Render all the faces
for (int face = 0; face < numFaces; face++) {
// Set the color for each of the faces
gl.glColor4f(colors[face][0], colors[face][1], colors[face][2], colors[face][3]);
// Draw the primitive from the vertex-array directly
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, face * 4, 4);
}
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisable(GL10.GL_CULL_FACE);
}
public float getPosX() {
return posX;
}
public void setPosX(float posX) {
this.posX = posX;
}
public float getPosY() {
return posY;
}
public void setPosY(float posY) {
this.posY = posY;
}
public float getPosZ() {
return posZ;
}
public void setPosZ(float posZ) {
this.posZ = posZ;
}
public float getAngleX() {
return angleX;
}
public void setAngleX(float angleX) {
this.angleX = angleX;
}
public float getAngleY() {
return angleY;
}
public void setAngleY(float angleY) {
this.angleY = angleY;
}
public float getAngleZ() {
return angleZ;
}
public void setAngleZ(float angleZ) {
this.angleZ = angleZ;
}

The code is ok. I think it's related to your device. Whether your device support OpenGLES1.1? Did you try to use some code like
mGlSurfaceView.setEGLContextClientVersion(1);
to define the version. Maybe the device's default OpenGLES version is 2.0(or the device do not support version 1.1). I am not sure about this, but I think it maybe an idea.

To draw tetrahedron using openGL in android with different color faces but Gray color face is getting distorted [closed]

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
package com.example.assignment1;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import javax.microedition.khronos.opengles.GL10;
public class Tetrahedron {
private FloatBuffer vertexBuffer; // Buffer for vertex-array
private int numFaces = 4;
//color codes for 4 faces
private float[][] colors = { // Colors of the 4 faces
{1.0f, 0.0f, 0.0f, 1.0f}, // 0. red
{1.0f, 1.0f, 1.0f, 1.0f}, // 1. white
{0.0f, 0.0f, 1.0f, 1.0f}, // 2. blue
{0.5019f, 0.5019f, 0.5019f, 1.0f}, // 3. grey
};
//coordinates of vertices of faces
//did i specified sequence correctly?
private float[] vertices = { // Vertices of the 4 faces
// FRONT Face
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
//Right face
-1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
// Left Face
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
// BOTTOM
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f
};
// Constructor - Set up the buffers
public Tetrahedron() {
// Setup vertex-array buffer. Vertices in float. An float has 4 bytes
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
vbb.order(ByteOrder.nativeOrder()); // Use native byte order
vertexBuffer = vbb.asFloatBuffer(); // Convert from byte to float
vertexBuffer.put(vertices); // Copy data into buffer
vertexBuffer.position(0); // Rewind
}
// Draw the shape
public void draw(GL10 gl) {
gl.glFrontFace(GL10.GL_CCW); // Front face in counter-clockwise orientation
//gl.glEnable(GL10.GL_CULL_FACE); // Enable cull face
gl.glCullFace(GL10.GL_BACK); // Cull the back face (don't display)
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
// Render all the faces
for (int face = 0; face < numFaces; face++) {
// Set the color for each of the faces
gl.glColor4f(colors[face][0], colors[face][1], colors[face][2], colors[face][3]);
// Draw the primitive from the vertex-array directly
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, face*4, 3);
}
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisable(GL10.GL_CULL_FACE);
}
}

gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, face*4, 3);
should probably be
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, face*3, 3);

Someone have code examples of a cube with different textures on each face? (OpenGL ES 1)

I need to understand how to put different textures on each face of a cube (OpenGL ES 1). But i can't find examples of how to do it
Atm i found an example of how to paint the same texture on all the faces of the cube, but i dont need that
this is the actual code i have:
public class Cube {
/** The buffer holding the vertices */
private FloatBuffer vertexBuffer;
/** The buffer holding the texture coordinates */
private FloatBuffer textureBuffer;
/** The buffer holding the indices */
private ByteBuffer indexBuffer;
/** Our texture pointer */
private int[] textures = new int[1];
/**
* The initial vertex definition
*
* Note that each face is defined, even
* if indices are available, because
* of the texturing we want to achieve
*/
private float vertices[] = {
//Vertices according to faces
-1.0f, -1.0f, 1.0f, //Vertex 0
1.0f, -1.0f, 1.0f, //v1
-1.0f, 1.0f, 1.0f, //v2
1.0f, 1.0f, 1.0f, //v3
1.0f, -1.0f, 1.0f, //...
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
};
/** The initial texture coordinates (u, v) */
private float texture[] = {
//Mapping coordinates for the vertices
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
};
/** The initial indices definition */
private byte indices[] = {
//Faces definition
0,1,3, 0,3,2, //Face front
4,5,7, 4,7,6, //Face right
8,9,11, 8,11,10, //...
12,13,15, 12,15,14,
16,17,19, 16,19,18,
20,21,23, 20,23,22,
};
/**
* The Cube constructor.
*
* Initiate the buffers.
*/
public Cube() {
//
ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
vertexBuffer = byteBuf.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
//
byteBuf = ByteBuffer.allocateDirect(texture.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
textureBuffer = byteBuf.asFloatBuffer();
textureBuffer.put(texture);
textureBuffer.position(0);
//
indexBuffer = ByteBuffer.allocateDirect(indices.length);
indexBuffer.put(indices);
indexBuffer.position(0);
}
/**
* The object own drawing function.
* Called from the renderer to redraw this instance
* with possible changes in values.
*
* #param gl - The GL Context
*/
public void draw(GL10 gl) {
//Bind our only previously generated texture in this case
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//Point to our buffers
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
//Set the face rotation
gl.glFrontFace(GL10.GL_CCW);
//Enable the vertex and texture state
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
//Draw the vertices as triangles, based on the Index Buffer information
gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer);
//Disable the client state before leaving
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
}
/**
* Load the textures
*
* #param gl - The GL Context
* #param context - The Activity context
*/
public void loadGLTexture(GL10 gl, Context context) {
//Get the texture from the Android resource directory
InputStream is = context.getResources().openRawResource(R.drawable.nehe);
Bitmap bitmap = null;
try {
//BitmapFactory is an Android graphics utility for images
bitmap = BitmapFactory.decodeStream(is);
} finally {
//Always clear and close
try {
is.close();
is = null;
} catch (IOException e) {
}
}
//Generate one texture pointer...
gl.glGenTextures(1, textures, 0);
//...and bind it to our array
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//Create Nearest Filtered Texture
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
//Different possible texture parameters, e.g. GL10.GL_CLAMP_TO_EDGE
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT);
//Use the Android GLUtils to specify a two-dimensional texture image from our bitmap
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);
//Clean up
bitmap.recycle();
}
}

You're drawing all 12 triangles of the cube with one call to glDrawElements. During one call to glDrawElements, the GL render state remains constant, and this includes the bound texture. Meaning, you can't change the texture used for rendering during the call to glDrawElements. So, to use different textures for each cube side, you need separate calls to glDrawElements. Before each call to it, you'll need to change the bound texture.
There are more advanced methods that would let you do it with a single call for efficiency but let's not bother with those for now.

OpenGL ES (Android) Cube disabling lighting when glEnable(GL_COLOR_MATERIAL) is added?

This is probably a really simple question, and I'm just not getting it. I'd like to have lighting on a cube, but have some faces have different colors. The following code results in a cube with no lighting, but one black face:
private float[] lightAmbient = { 1.0f, 1.0f, 1.0f, 1.0f };
private float[] lightDiffuse = { 1.0f, 1.0f, 1.0f, 1.0f };
private float[] lightPosition = { 0.0f, 0.0f, 3.0f, 1.0f};
float matAmbient[] = new float[] { 0.3f, 0.3f, 0.3f, 1.0f };
float matDiffuse[] = new float[] { 0.6f, 0.6f, 0.6f, 1.0f };
private FloatBuffer vertexBuffer;
private FloatBuffer normalBuffer;
private FloatBuffer colorBuffer;
float vertices[] = new float[] {
// FRONT
-0.5f, -0.5f, 0.5f,
0.5f, -0.5f, 0.5f,
-0.5f, 0.5f, 0.5f,
0.5f, 0.5f, 0.5f,
// BACK
-0.5f, -0.5f, -0.5f,
-0.5f, 0.5f, -0.5f,
0.5f, -0.5f, -0.5f,
0.5f, 0.5f, -0.5f,
// LEFT
-0.5f, -0.5f, 0.5f,
-0.5f, 0.5f, 0.5f,
-0.5f, -0.5f, -0.5f,
-0.5f, 0.5f, -0.5f,
// RIGHT
0.5f, -0.5f, -0.5f,
0.5f, 0.5f, -0.5f,
0.5f, -0.5f, 0.5f,
0.5f, 0.5f, 0.5f,
// TOP
-0.5f, 0.5f, 0.5f,
0.5f, 0.5f, 0.5f,
-0.5f, 0.5f, -0.5f,
0.5f, 0.5f, -0.5f,
// BOTTOM
-0.5f, -0.5f, 0.5f,
-0.5f, -0.5f, -0.5f,
0.5f, -0.5f, 0.5f,
0.5f, -0.5f, -0.5f,
};
float colors[] = new float[] {
// FRONT
0.0f, 0.0f, 0.0f, 0.0f,
0.0f, 0.0f, 0.0f, 0.0f,
0.0f, 0.0f, 0.0f, 0.0f,
0.0f, 0.0f, 0.0f, 0.0f,
// BACK
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
// LEFT
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
// RIGHT
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
// TOP
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
// BOTTOM
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
};
float normals[] = new float[] {
// FRONT
0f, 0f, 1f,
0f, 0f, 1f,
0f, 0f, 1f,
0f, 0f, 1f,
// BACK
0f, 0f, -1f,
0f, 0f, -1f,
0f, 0f, -1f,
0f, 0f, -1f,
// LEFT
-1f, 0f, 0f,
-1f, 0f, 0f,
-1f, 0f, 0f,
-1f, 0f, 0f,
// RIGHT
1f, 0f, 0f,
1f, 0f, 0f,
1f, 0f, 0f,
1f, 0f, 0f,
// TOP
0f, 1f, 0f,
0f, 1f, 0f,
0f, 1f, 0f,
0f, 1f, 0f,
// BOTTOM
0f, -1f, 0f,
0f, -1f, 0f,
0f, -1f, 0f,
0f, -1f, 0f
};
...
gl.glEnable(GL10.GL_LIGHTING);
gl.glEnable(GL10.GL_LIGHT0);
gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_AMBIENT, matAmbient, 0);
gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_DIFFUSE, matDiffuse, 0);
gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_AMBIENT, lightAmbient, 0);
gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_DIFFUSE, lightDiffuse, 0);
gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_POSITION, lightPosition, 0);
gl.glEnable(GL10.GL_DEPTH_TEST);
gl.glDepthFunc(GL10.GL_LEQUAL);
gl.glEnable(GL10.GL_CULL_FACE);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glEnable(GL10.GL_COLOR_MATERIAL);
gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
gl.glClearDepthf(1.0f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glNormalPointer(GL10.GL_FLOAT, 0, normalBuffer);
gl.glEnableClientState(GL10.GL_NORMAL_ARRAY);
gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
}
public GLScreen(Context context) {
super(context);
this.setRenderer(this);
this.requestFocus();
vertexBuffer = makeFloatBuffer(vertices);
normalBuffer = makeFloatBuffer(normals);
colorBuffer = makeFloatBuffer(colors);
}
float xrot = 0.0f;
float yrot = 0.0f;
#Override
public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
GLU.gluLookAt(gl, 0, 0, 3, 0, 0, 0, 0, 1, 0);
gl.glRotatef(xrot, 1, 0, 0);
gl.glRotatef(yrot, 0, 1, 0);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 4, 4);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 8, 4);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 12, 4);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 16, 4);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 20, 4);
xrot += 1.0f;
yrot += 0.5f;
}
Uncommenting glEnable(GL10.GL_COLOR_MATERIAL) results in a lighted cube with no black face. How would I get a lighted cube with one black face?

I think here you'll find the answer. Both Android Emulator and HTC phones (I don't know about others, I haven't tested apps on them) have bugs with lighting.

Texture coordinates in opengl android showing image reversed

I wrote opengl android code to show a bitmap on a square. But bitmap was drawn in reverse. When i change texture array combination to the commented code it is drawn correctly. But i insist my texture array must be as below . Am i thinking wrong ?
/** The initial vertex definition */
private float vertices[] = {
-1.0f, 1.0f, 0.0f, //Top Left
-1.0f, -1.0f, 0.0f, //Bottom Left
1.0f, -1.0f, 0.0f, //Bottom Right
1.0f, 1.0f, 0.0f //Top Right
};
/** Our texture pointer */
private int[] textures = new int[1];
/** The initial texture coordinates (u, v) */
private float texture[] = {
//Mapping coordinates for the vertices
// 1.0f, 0.0f,
// 1.0f, 1.0f,
// 0.0f, 1.0f,
// 0.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,
1.0f, 0.0f,
1.0f, 1.0f,
};
/** The initial indices definition */
private byte indices[] = {
//2 triangles
0,1,2, 2,3,0,
};

Whereas Android uses the top-left corner as being 0,0 of the coordinate system, OpenGL uses the bottom-left corner being 0,0 which is why your texture gets flipped.
A common solution to this is to flip your texture at load time,
Matrix flip = new Matrix();
flip.postScale(1f, -1f);
Bitmap bmp = Bitmap.createBitmap(resource, 0, 0, resource.getWidth(), resource.getHeight(), flip, true);

Actually, I think Will Kru's solution should have flipped the background around both axes
flip.postScale(-1f, -1f);
That solution worked for me!

This worked for me. (no need to create another bitmap and scale)
private float vertices[] = {
1.0f, -1.0f, 0.0f, //Bottom Right
1.0f, 1.0f, 0.0f, //Top Right
-1.0f, 1.0f, 0.0f, //Top Left
-1.0f, -1.0f, 0.0f, //Bottom Left
};

Develop Reference

The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.

OpenGL drawing a Hexigon with vertices - android

Should be private float verticesFlat[] = { 0.0f, 0.0f, 0.0f, //center -0.5f, 1.0f, 0.0f, // left top 0.5f, 1.0f, 0.0f, // right top 1.0f, 0.0f, 0.0f, // right 0.5f, -1.0f, 0.0f, // right bottom (notice sign) -0.5f, -1.0f, 0.0f, // left bottom -1.0f, 0.0f, 0.0f, // left };

Related

Android OpenGLES - Cube not showing on some devices

To draw tetrahedron using openGL in android with different color faces but Gray color face is getting distorted [closed]

Someone have code examples of a cube with different textures on each face? (OpenGL ES 1)

OpenGL ES (Android) Cube disabling lighting when glEnable(GL_COLOR_MATERIAL) is added?

Texture coordinates in opengl android showing image reversed

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