Develop Reference

How to hold the shape when i rotate a texture through matrix using OpenGL ES 2.0

This is my VertexShader:
public static final String vs_Face =
"uniform mat4 transMatrix;" +
"uniform mat4 scaleMatrix;" +
"uniform mat4 rotateZMatrix;" +
"attribute vec4 vPosition;" +
"attribute vec2 a_texCoord;" +
"varying vec2 v_texCoord;" +
"void main() {" +
" gl_Position = transMatrix * rotateZMatrix *scaleMatrix * vec4(vPosition.xyz,1.0) ;" +
" v_texCoord = a_texCoord.xy;" +
"}";
This my FragmentShader:
public static final String fs_Face =
"precision mediump float;" +
"varying vec2 v_texCoord;" +
"uniform sampler2D s_texture;" +
"void main() {" +
" gl_FragColor = texture2D( s_texture, v_texCoord );" +
"}";
This is my Draw function
GLES20.glEnable(GLES20.GL_BLEND);
GLES20.glBlendFunc(GLES20.GL_ONE,GLES20.GL_ONE_MINUS_SRC_ALPHA);
//
GLES20.glUseProgram(mProgramMagic);
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, mGLCubeId[0]);
GLES20.glEnableVertexAttribArray(mPositionHandleFace);
GLES20.glVertexAttribPointer(mPositionHandleFace, 2, GLES20.GL_FLOAT, false, 0, 0);
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, mMagicTextureCoordinateId[0]);
GLES20.glEnableVertexAttribArray ( mTexCoordLocFace );
GLES20.glVertexAttribPointer(mTexCoordLocFace, 2, GLES20.GL_FLOAT, false, 4 * 2, 0);
//control matrix
GLES20.glUniformMatrix4fv(mTransHandle,1,false,transMatrix,0);
GLES20.glUniformMatrix4fv(mScaleHandle,1,false,scaleMatrix,0);
GLES20.glUniformMatrix4fv(mMvpMatrixHandle,1,false,mvpMatrix,0);
GLES20.glUniformMatrix4fv(mRotateZHandle,1,false,rotateZMatrix,0);
GLES20.glUniformMatrix4fv(mTransZeroMatrixHandle, 1, false, mTransZeroMatrix, 0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D,mTextures[0]);
if(i>=mTotalCount)
{
i=i-mTotalCount;
}
// update texture
if(mPathList.size()-1>=i&&mTextureMap.containsKey(mPathList.get(i)))
{
GLUtils.texSubImage2D(GLES20.GL_TEXTURE_2D,0,0,0,mTextureMap.get(mPathList.get(i)));
}
GLES20.glUniform1i ( mSamplerLocFace, 0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
// Disable vertex array
GLES20.glDisableVertexAttribArray(mPositionHandleFace);
GLES20.glDisableVertexAttribArray(mTexCoordLocFace);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D,0);
If I dont add the rotateZ matrix like this: gl_Position =vec4(vPosition.xyz,1.0) ,the texture can display properly. but after i add the rotateZMatrix,its shape will change.
This is the picture after i rotate 45 degrees,the rabbit ears and noise is the texture:
Picture
I don't know what i did wrong,I have tried multiple variations of this, but none of them seem to work.

android : Error on Shading Language with opengl es2.0 on android 2.2

I have a problem with application. is a simple application atm using opengl es2.0 which running on android 2.2 device HTC sense. I can running the application on my 4.0.3 emulator as well as my device which running android 4.0.
When running on android 2.2, i have this error:
> FATAL EXCEPTION: GLThread 9
java.lang.RuntimeException: Error compiling shader:
SimpleShader.loadShader(SimpleShader.java:87)
SimpleShader.<init>(SimpleShader.java:54)
etc
I assumed that the device can run android 2.2 as the document told LINKS TO DOCUMENTATION, but not sure about the shader part though.
Here is my shader code:
String verticesShader =
"uniform mat4 uScreen;\n" +
"attribute vec2 aPosition;\n" +
"attribute vec3 aColor;\n" +
"attribute vec2 aTexPos; \n" +
"varying vec2 vTexPos; \n" +
"varying vec3 vColor;\n" +
"void main() {\n" +
" vTexPos = aTexPos; \n" +
" gl_Position = uScreen * vec4(aPosition.xy, 0.0, 1.0);\n" +
" vColor = aColor;\n" +
"}";
// Our fragment shader. Just return vColor.
// If you look at this source and just said 'WTF?', remember
// that all the attributes are defined in the VERTEX shader and
// all the 'varying' vars are considered OUTPUT of vertex shader
// and INPUT of the fragment shader. Here we just use the color
// we received and add a alpha value of 1.
String fragmentShader =
"uniform float uUseTexture; \n" +
"uniform float uAlpha; \n" +
"uniform sampler2D uTexture;\n" +
"precision mediump float;\n"+
"varying vec2 vTexPos; \n" +
"varying vec3 vColor;\n" +
"void main(void)\n" +
"{\n" +
" if ( uUseTexture != 1.0 ) \n" +
" gl_FragColor = vec4(vColor.xyz, 1); \n" +
" else \n" +
" gl_FragColor = texture2D(uTexture, vTexPos); \n" +
" gl_FragColor.a *= uAlpha;" +
//" gl_FragColor = vec4(vColor.xyz, 1);\n" +
"}";
private int loadShader(int shader, String shaderSrc) {
// TODO Auto-generated method stub
int handle = GLES20.glCreateShader(shader);
if (handle == GLES20.GL_FALSE)
throw new RuntimeException("Error creating shader!");
GLES20.glShaderSource(handle, shaderSrc);
GLES20.glCompileShader(handle);
int[] compileStatus = new int[1];
GLES20.glGetShaderiv(handle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
if (compileStatus[0] ==0)
{
String error = GLES20.glGetShaderInfoLog(handle);
GLES20.glDeleteShader(handle);
throw new RuntimeException("Error compiling shader: " + error);
}
else
return handle;
}
The application works fine on my latest device with android 4.0+

Have you considered checking your OpenGL ES GLSL version on both the android 2.2 device and the android 4.0+ device?
You can print it with GLES20.glGetString(GLES20.GL_SHADING_LANGUAGE_VERSION).

How do I draw a triangle using a solid color without interpolation in the fragment shader?

This should really be a simple task, but I fail miserably. First a confession: I know very little about OpenGL and the few things I've learned come from various tutorials (some of which are probably outdated and deprecated)
I'm trying to draw a quad using a single color defined at runtime. The quad is drawn in the correct size and position but with the wrong color. This is my vertex and fragment shader:
public static final String VS_SOLIDCOLOR =
"uniform mat4 uMVPMatrix;" +
"attribute vec4 aPosition;" +
"attribute vec4 aColor;" +
"varying vec4 vColor;" +
"void main() {" +
" gl_Position = uMVPMatrix * aPosition;" +
" vColor = aColor;" +
"}";
public static final String FS_SOLIDCOLOR =
"precision mediump float;" +
"varying vec4 vColor;" +
"void main() {" +
" gl_FragColor = vColor;" +
"}";
The color is set like this (I have removed gl error check and check for colorHandle == -1):
float r = 1.0f;
float g = 0.0f;
float b = 0.0f;
float a = 1.0f;
final int colorHandle = GLES20.glGetAttribLocation(shaderProgramSolidColor, "aColor");
GLES20.glVertexAttrib4f(colorHandle, r, g, b, a);
I would have expected the above code to result in solid red triangles, but they end up as solid yellow. From what I've read the fragment shader will interpolate the vColor vector, but I don't want that (and I'm not sure why it ends up as yellow). How do I set a color at runtime and get that drawn unchanged on my triangles?
PS If I were to do this in the fragment shader I would get a solid red color for my entire quad:
gl_FragColor = vec4(1,0,0,1);
Let me know if you need me to post more code.

I found what I did wrong. I was under the impression that I could only set variables in the vertex shader at runtime, but it's possible to manipulate the fragment shader as well. My shader should look like this:
public static final String VS_SOLIDCOLOR =
"uniform mat4 uMVPMatrix;" +
"attribute vec4 aPosition;" +
"void main() {" +
" gl_Position = uMVPMatrix * aPosition;" +
"}";
public static final String FS_SOLIDCOLOR =
"precision mediump float;" +
"uniform vec4 uColor;" +
"void main() {" +
" gl_FragColor = uColor;" +
"}";
And set like this:
final int colorHandle = GLES20.glGetUniformLocation(shaderProgramSolidColor, "uColor");
GLES20.glUniform4f(colorHandle, r, g, b, a);

Opengl es 2.0 trying to pass a float value to fragment shader android

How can I pass a float value to fragment shader ?
This is my code on android:
int aUseTexture = GLES20.glGetAttribLocation(program, "uUseTexture");
GLES20.glUniform1f(aUseTexture, 1.0f);
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
Here is my shader:
String verticesShader =
"uniform mat4 uScreen;\n" +
"attribute vec2 aPosition;\n" +
"attribute vec3 aColor;\n" +
"attribute vec2 aTexPos; \n" +
"varying vec2 vTexPos; \n" +
"varying vec3 vColor;\n" +
"void main() {\n" +
" vTexPos = aTexPos; \n" +
" gl_Position = uScreen * vec4(aPosition.xy, 0.0, 1.0);\n" +
" vColor = aColor;\n" +
"}";
// Our fragment shader. Just return vColor.
// If you look at this source and just said 'WTF?', remember
// that all the attributes are defined in the VERTEX shader and
// all the 'varying' vars are considered OUTPUT of vertex shader
// and INPUT of the fragment shader. Here we just use the color
// we received and add a alpha value of 1.
String fragmentShader =
"uniform float uUseTexture; \n" +
"uniform sampler2D uTexture;\n" +
"precision mediump float;\n"+
"varying vec2 vTexPos; \n" +
"varying vec3 vColor;\n" +
"void main(void)\n" +
"{\n" +
" if ( uUseTexture != 1.0 ) \n" +
" gl_FragColor = vec4(vColor.xyz, 1); \n" +
" else \n" +
" gl_FragColor = texture2D(uTexture, vTexPos); \n" +
//" gl_FragColor = vec4(vColor.xyz, 1);\n" +
"}";
You can see the if statement in the fragment shader , that is the one i tried to check if i pass in 1.0 it should do texture else use color.

You are probably using the wrong function call for "uniform variable". Try glGetUniformLocation() as follow:
int aUseTexture = GLES20.glGetUniformLocation(program, "uUseTexture");
Also, the floating point testing (uUseTexture != 1.0) may not be always reliable all the time. You may want to use an integer type.

As far as I know you have to pass the value through the vertex shader before it can get to the fragment shader. e.g. add "uniform float uUseTexture_in; \n" and "varying float uUseTexture; \n" at the top of the vertex shader, in the main function add "uUseTexture = uUseTexture_in;". And your shader should work

LibGDX - Create complex textured object using shaders (OpenGL ES 2.0)

I'm trying to create 3D scene. There is textured Earth with clouds. I think that clouds I will be able to create by transparent sphere and texture of clouds on it(if I'm wrong please correct me). So I have some code below:
ShaderProgram shader;
Mesh mesh, cloudMesh;
Texture texture, cloudTexture;
Matrix4 matrix = new Matrix4();
public void create() {
String vertexShader = "attribute vec4 a_position; \n"
+ "attribute vec4 a_color;\n"
+ "attribute vec2 a_texCoords;\n"
+ "uniform mat4 u_worldView;\n"
+ "varying vec4 v_color;"
+ "varying vec2 v_texCoords;"
+ "void main() \n"
+ "{ \n"
+ " v_color = vec4(1, 1, 1, 1); \n"
+ " v_texCoords = a_texCoords; \n"
+ " gl_Position = u_worldView * a_position; \n"
+ "} \n";
String fragmentShader = "#ifdef GL_ES\n"
+ "precision mediump float;\n"
+ "#endif\n"
+ "varying vec4 v_color;\n"
+ "varying vec2 v_texCoords;\n"
+ "uniform sampler2D u_texture;\n"
+ "void main() \n"
+ "{ \n"
+ " gl_FragColor = v_color * texture2D(u_texture, v_texCoords);\n"
+ "}";
shader = new ShaderProgram(vertexShader, fragmentShader);
if (shader.isCompiled() == false) {
System.exit(0);
}
mesh = ObjLoader.loadObj(Gdx.files.internal("objects/earth.obj").read());
cloudMesh = ObjLoader.loadObj(Gdx.files.internal("objects/cloud_sphere.obj").read());
texture = new Texture(Gdx.files.internal("images/earthmap.jpg"));
cloudTexture = new Texture(Gdx.files.internal("images/earth_clouds_map.jpg"));
}
public void render() {
angle += Gdx.graphics.getDeltaTime() * 30;
matrix.setToRotation(axis, angle);
Gdx.graphics.getGL20().glViewport(-10, 10, Gdx.graphics.getWidth(),
Gdx.graphics.getHeight());
Gdx.graphics.getGL20().glClearColor(0.2f, 0.2f, 0.2f, 1);
Gdx.graphics.getGL20().glClear(GL20.GL_COLOR_BUFFER_BIT);
Gdx.graphics.getGL20().glEnable(GL20.GL_TEXTURE_2D);
Gdx.graphics.getGL20().glEnable(GL20.GL_BLEND);
Gdx.graphics.getGL20().glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);
texture.bind();
shader.begin();
shader.setUniformMatrix("u_worldView", matrix);
shader.setUniformi("u_texture", 0);
mesh.render(shader, GL20.GL_TRIANGLE_STRIP);
shader.end();
//SHOULD I USE SHADER PROGRAM LIKE BELOW?
cloudTexture .bind();
shader.begin();
shader.setUniformMatrix("u_worldView", matrix);
shader.setUniformi("u_texture", 0);
cloudMesh.render(shader, GL20.GL_TRIANGLE_STRIP);
shader.end();
}
So I don't see any textures on spheres. Where is mistake? If someone have any ideas, links or examples it will be appreciated!

Before loading your textures you have to define a "slot" where your texture will be stored:
Gdx.graphics.getGL20().glActiveTexture(GL20.GL_TEXTURE0);
texture = new Texture(Gdx.files.internal("images/earthmap.jpg"));
texture.bind();
Gdx.graphics.getGL20().glActiveTexture(GL20.GL_TEXTURE1);
cloudTexture = new Texture(Gdx.files.internal("images/earth_clouds_map.jpg"));
cloudTexture.bind();
in your render-method you then bind the texture and assign it to the shader using these "slots"
shader.setUniformi("u_texture", 0);
...
...
shader.setUniformi("u_texture", 1);
that should be all...