Develop Reference

creating a framebuffer to take an image from external oes

I am trying to do multi pass rendering with framebuffer the issue is that the source is the camera so the texInput is not of type GL_TEXTURE_2D it is of type GL_TEXTURE_EXTERNAL_OES tho, if I use the function glTexImage2D it gives a black screen when I use that texture in the future after rendering to it without any errors glErros.
On the other hand if I don't use it(because it does not support GL_TEXTURE_EXTERNAL_OES) it gives me framebuffer status of NOT_COMPLETE
here is my code for creating the framebuffer and the texture that I want to associate to it.
fun prepareFBO() {
val intArray = IntArray(1)
glGenFramebuffers(1, intArray, 0)
fboId = intArray.first()
glGenTextures(1, intArray, 0)
texId = intArray.first()
glBindTexture(GL_TEXTURE_2D, texId)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,1080, 1920, 0, GL_RGBA, GL_UNSIGNED_BYTE, null)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
glBindFramebuffer(GL_FRAMEBUFFER, fboId)
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texId, 0)
val status = glCheckFramebufferStatus(GL_FRAMEBUFFER)
Log.e(TAG, "prepareFBO: ${status == GL_FRAMEBUFFER_COMPLETE}")
glBindFramebuffer(GL_FRAMEBUFFER, 0)
glBindTexture(GL_TEXTURE_2D, 0)
}
the rest is just normal glDrawArrays and glActiveTexture that already works fine when I draw directly to the default framebuffer, if needed please let me know and I will share them.
Thanks for help!
UPDATE:
I found that I need instead of using glTexImage2d I can use eglBindTexImage instead so the final code is:
fun prepareFBO() {
val intArray = IntArray(1)
glGenFramebuffers(1, intArray, 0)
fboId = intArray.first()
glBindFramebuffer(GL_FRAMEBUFFER, fboId)
glGenTextures(1, intArray, 0)
texId = intArray.first()
glBindTexture(GL_TEXTURE_EXTERNAL_OES, texId)
checkGlError("Error 1")
eglBindTexImage(eglGetCurrentDisplay(), windowSurface!!.eglSurface, EGL_BACK_BUFFER)
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_EXTERNAL_OES, texId, 0)
val status = glCheckFramebufferStatus(GL_FRAMEBUFFER)
Log.e(TAG, "prepareFBO: is status complete? => ${status == GL_FRAMEBUFFER_COMPLETE}")
}
while this looks like it makes sense, still I am getting the status of the framebuffer as not complete :/

Render to texture attached to Frame Buffer Object (texture appears black)

I have generated a frame buffer object(FBO), bind it, attached a texture to its GL_COLOR_ATTACHMENT0. Then ensure that I get its status as GL_FRAMEBUFFER_COMPLETE. I have another texture(which is displaying on display), let's call it workingTexture. Now I want to render this workingTexture onto FBO, so I bind this FBO and then render workingTexture.
Then I bind default frame buffer(reserved for display) and try to render the texture attached to FBO, thinking that I will get my texture onto display, but I get black texture.
Relevant code
code to generate workingTexture...
int[] workingTexture = new int[1];
glGenTextures(1, workingTexture, 0); // generate workingTexture
glActiveTexture(GL_TEXTURE0); // attach it to TEXTURE_UNIT0
glBindTexture(GL_TEXTURE_2D, workingTexture[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_MIRRORED_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_MIRRORED_REPEAT);
code to generate fbo
int[] fboName = new int[1];
int[] fboTextureName = new int[1];
final int fboTextureUnit = 1; // attach this texture to texture unit GL_TEXTURE1
glGenFramebuffers(1, fboName, 0);
int generatedTextureNameForFBO =
generateTextureForFBO(fboTextureUnit,
width, height);
fboTextureName[0] = generatedTextureNameForFBO;
glBindFramebuffer(GL_FRAMEBUFFER, fboName[0]);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D, generatedTextureNameForFBO, 0);
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
// created FBO is not complete
throw new RuntimeException("FBO status INCOMPLETE 😔😔");
}
method used to generate texture attached to fbo
private int generateTextureForFBO(#IntRange(from = 0) final int textureUnit,
#IntRange(from = 1) final int width,
#IntRange(from = 1) final int height) {
int[] textureName = new int[1];
glGenTextures(1, textureName, 0);
glActiveTexture(GL_TEXTURE0 + textureUnit);
glBindTexture(GL_TEXTURE_2D, textureName[0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, null);
// glBindTexture(GL_TEXTURE_2D, 0);
// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_MIRRORED_REPEAT);
// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_MIRRORED_REPEAT);
// glBindTexture(GL_TEXTURE_2D, 0);
return textureName[0];
}
Now coming to drawing part...
#Override
public void onDrawFrame(GL10 unused) {
glClear(GL_COLOR_BUFFER_BIT);
//renderTex(mViewMatrix, 0, texProgram); // this texture is drawing on screen
glBindFramebuffer(GL_FRAMEBUFFER, fboName[0]);
renderTex(mViewMatrix, 0, texProgram); // rendering workingTexture onto FBO
glBindFramebuffer(GL_FRAMEBUFFER, 0);
renderTex(mViewMatrix, fboTextureUnit[0], texProgram); // texture appears black
}
renderTex is a simple method to render texture. It is working fine.
Also I have checked for GL_ERROR but there is no error.
My understanding of application created FBO is that every read and write glCall will happen on currently bound FBO, so is my understanding of FBO incorrect, or is there some error in my code.
Platform OpenGL|es 20 on Android

The texture which is generated in generateTextureForFBO is mipmap incomplete.
If you do not generate mipmaps (by glGenerateMipmap), then setting the GL_TEXTURE_MIN_FILTER is important. Since the default filter is GL_NEAREST_MIPMAP_LINEAR the texture would be mipmap incomplete, if you don not change the minifying function to GL_NEAREST or GL_LINEAR.
Set the texture minifying function (GL_TEXTURE_MIN_FILTER) by glTexParameter:
glBindTexture(GL_TEXTURE_2D, textureName[0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, null);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

Cubemap texture with bitmap in OpenGL ES 2.0/3.0

When I create a cubemap texture with simple colors, this works well:
#JvmStatic
fun createSimpleTextureCubemap() {
val textureId = IntArray(1)
val cubeFace0 = byteArrayOf(127, 127, 127)
val cubeFace1 = byteArrayOf(0, 127, 0)
... // create other cube faces with simple color
val cubeFaces = ByteBuffer.allocateDirect(3)
glGenTextures(1, textureId, 0)
glBindTexture(GL_TEXTURE_CUBE_MAP, textureId[0])
cubeFaces.put(cubeFace0).position(0)
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB,
1, 1, 0, GL_RGB, GL_UNSIGNED_BYTE, cubeFaces)
cubeFaces.put(cubeFace1).position(0)
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB,
1, 1, 0, GL_RGB, GL_UNSIGNED_BYTE, cubeFaces)
...
return textureId[0]
}
But when I try to create a cubemap texture with bitmap:
#JvmStatic
fun createTextureCubemap(context: Context, rowID: Int) {
val input = context.resources.openRawResource(rowID)
val bitmap = BitmapFactory.decodeStream(input)
val textureId = IntArray(1)
glGenTextures(1, textureId, 0)
glBindTexture(GL_TEXTURE_CUBE_MAP, textureId[0])
GLUtils.texImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, bitmap, 0)
GLUtils.texImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, bitmap, 0)
GLUtils.texImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, bitmap, 0)
GLUtils.texImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, bitmap, 0)
GLUtils.texImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, bitmap, 0)
GLUtils.texImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, bitmap, 0)
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
return textureId[0]
}
Then the object turns black. Someone may suggest why the cubemap with the bitmap does not work (black color)?
Thanks for any comment/answer.

Textures for Cubemaps need to be square. As mentioned in the comments, the bitmap used was not square.
From glTexImage2D reference (GLUtils.texImage2D is a convenience wrapper around glTexImage2D)
GL_INVALID_VALUE is generated if target is one of the six cube map 2D image targets and the width and height parameters are not equal.

Why would an OpenGL ES render on iOS be flipped vertically?

I've got some C code to render some OpenGL stuff and it's running on both Android and iOS. On Android it looks fine. But on iOS it is flipped vertically.
Here's some simple code to demonstrate (only copied the relevant parts because OpenGL C code is long-winded):
GLfloat vVertices[] = {
0.0f, 0.5f,
-0.5f, -0.5f,
0.5f, -0.5f
};
glViewport(0, 0, context->width, context->height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(data->programObject);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vVertices);
glEnableVertexAttribArray(0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
On Android it looks like this:
But on iOS it looks like this:
The only thing that differs between the two platforms is the initialization code for OpenGL ES, since all the OpenGL code is shared C code. However, I can't spot anything obviously wrong with the init code.
Here's the init code (I removed most error handling because there are no errors being triggered apart from the one I left in):
- (void)initGL {
_context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
[EAGLContext setCurrentContext:_context];
[self createCVBufferWithSize:_renderSize withRenderTarget:&_target withTextureOut:&_texture];
glBindTexture(CVOpenGLESTextureGetTarget(_texture), CVOpenGLESTextureGetName(_texture));
glTexImage2D(GL_TEXTURE_2D, // target
0, // level
GL_RGBA, // internalformat
_renderSize.width, // width
_renderSize.height, // height
0, // border
GL_RGBA, // format
GL_UNSIGNED_BYTE, // type
NULL); // data
// HACK: we always get an "error" here (GL_INVALID_OPERATION) despite everything working. See https://stackoverflow.com/questions/57104033/why-is-glteximage2d-returning-gl-invalid-operation-on-ios
glGetError();
glGenRenderbuffers(1, &_depthBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _depthBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, _renderSize.width, _renderSize.height);
glGenFramebuffers(1, &_frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, _frameBuffer);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, CVOpenGLESTextureGetName(_texture), 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthBuffer);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
NSLog(#"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
} else {
NSLog(#"Successfully initialized GL");
char* glRendererName = getGlRendererName();
char* glVersion = getGlVersion();
char* glShadingLanguageVersion = getGlShadingLanguageVersion();
NSLog(#"OpenGL renderer name: %s, version: %s, shading language version: %s", glRendererName, glVersion, glShadingLanguageVersion);
}
}
And here's the code that creates the actual texture (using EAGL):
- (void)createCVBufferWithSize:(CGSize)size
withRenderTarget:(CVPixelBufferRef *)target
withTextureOut:(CVOpenGLESTextureRef *)texture {
CVReturn err = CVOpenGLESTextureCacheCreate(kCFAllocatorDefault, NULL, _context, NULL, &_textureCache);
if (err) return;
CFDictionaryRef empty;
CFMutableDictionaryRef attrs;
empty = CFDictionaryCreate(kCFAllocatorDefault,
NULL,
NULL,
0,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
attrs = CFDictionaryCreateMutable(kCFAllocatorDefault, 1,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
CFDictionarySetValue(attrs, kCVPixelBufferIOSurfacePropertiesKey, empty);
CVPixelBufferCreate(kCFAllocatorDefault, size.width, size.height,
kCVPixelFormatType_32BGRA, attrs, target);
CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
_textureCache,
*target,
NULL, // texture attributes
GL_TEXTURE_2D,
GL_RGBA, // opengl format
size.width,
size.height,
GL_BGRA, // native iOS format
GL_UNSIGNED_BYTE,
0,
texture);
CFRelease(empty);
CFRelease(attrs);
}
Can anyone tell me why iOS is flipped like this? I've since noticed other people with the same problem, such as here but haven't found a solution yet.

Android OpenGL UV mapping error after triangulating

I'm building an Android app to render 3d (wavefront.obj) model. By using tinyobjloader, I can successfully load the model.
Code:
std::vector<glm::vec3> vertices;
std::vector<glm::vec2> uvs;
std::vector<glm::vec3> normals;
tinyobj::attrib_t attrib;
std::vector<tinyobj::shape_t> shapes;
std::vector<tinyobj::material_t> materials;
for(size_t s =0; s < shapes.size(); s++)
{
size_t index_offset = 0;
for(size_t f = 0; f < shapes[s].mesh.num_face_vertices.size(); f++)
{
int fv = shapes[s].mesh.num_face_vertices[f];
for(size_t v = 0; v < fv; v++)
{
tinyobj::index_t idx = shapes[s].mesh.indices[index_offset + v];
tinyobj::real_t vx = attrib.vertices[3*idx.vertex_index+0];
tinyobj::real_t vy = attrib.vertices[3*idx.vertex_index+1];
tinyobj::real_t vz = attrib.vertices[3*idx.vertex_index+2];
tinyobj::real_t nx = attrib.normals[3*idx.normal_index+0];
tinyobj::real_t ny = attrib.normals[3*idx.normal_index+1];
tinyobj::real_t nz = attrib.normals[3*idx.normal_index+2];
tinyobj::real_t ux = attrib.texcoords[2*idx.texcoord_index+0];
tinyobj::real_t uy = attrib.texcoords[2*idx.texcoord_index+1];
vertices.push_back(glm::vec3(vx,vy,vz));
normals.push_back(glm::vec3(nx,ny,nz));
uvs.push_back(glm::vec2(ux,uy));
}
index_offset += fv;
}
}
Because the original .obj file has multiple faces format, i.e:
f 1/2/3 3/2/1 3/2/3
f 1/2/3 1/3/4 1/4/5 6/7/2
so that I use Blender Triangulate with 'Beauty' option to convert quad to triangle. But the rendered result is weird
I have built two function to initOpenGL (run once) and render().
initOpenGL code:
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(glm::vec3), &vertices[0], GL_STATIC_DRAW);
glGenBuffers(1, &UVBO);
glBindBuffer(GL_ARRAY_BUFFER, UVBO);
glBufferData(GL_ARRAY_BUFFER, uvs.size() * sizeof(glm::vec2), &uvs[0], GL_STATIC_DRAW);
//Linking Vertex Attribute
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
//bind texture
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, UVBO);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);
//load texture
//texture1
glGenTextures(1, &texture1);
glBindTexture(GL_TEXTURE_2D, texture1);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
if(patternSrc1)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, patWidth1, patHeight1, 0, GL_RGBA, GL_UNSIGNED_BYTE,
patternSrc1);
//glGenerateMipmap(GL_TEXTURE_2D);
}
render() code:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(shaderProgram);
camera.ProcessOneFinger(moveStpX, moveStpY);
camera.ProcessTwoFinger(move2X, move2Y);
projection = glm::perspective(camera.GetZoom(), (GLfloat)600/(GLfloat)1024, nearPlane, farPlane);
view = camera.GetViewMatrix();
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "view"), 1, GL_FALSE, glm::value_ptr(view));
glm::mat4 model;
model = glm::translate(model, glm::vec3(0.0f, 0.0f, 0.0f));
GLfloat angle = 20.0f;
model = glm::rotate(model, angle, glm::vec3( 1.0f, 0.3f, 0.5f));
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "model"), 1, GL_FALSE, glm::value_ptr( model ) );
glDrawArrays(GL_TRIANGLES, 0, vertices.size());
Model detail
Texture:
Model.obj file after triangulated:
https://pastebin.com/vUjHv8Fr
Thank you!!!

This looks to me like your texture is upside down. There's basically two potential errors that could each lead to this happening. Most likely, the texture image itself is upside down, e.g., because the image data passed to glTexImage2D() is in the wrong order. Unlike most other APIs, OpenGL (by default) expects pixel data in row-wise order starting from the bottom row. Check the way you load the texture data to make sure it's in the right order.
If this is not the problem, then it might be that your texture coordinates are for a left-handed texture coordinate system. OpenGL, however, uses right-handed texture coordinates where the origin is the lower-left corner of the texture image rather than the upper left corner. I'm not a Blender guy, but there's probably an export setting for this…