OpenGL Framebuffer Render to Texture not Working

Question

I'm experimenting with framebuffers to create a glow effect using Java and JOGL, but I am having problems. At the moment, my goal is to render my spaceship model, textured with an illumination texture, to a framebuffer texture and then draw the framebuffer texture to a triangle fan quad. I'm running with OpenGL 2.1 and/or 2.0 Here is my code for generating the framebuffer and its texture:

private int createFrameBuffer(GL2GL3 gl) {
    _frameBufferTextureId = GLHelper.makeTextureBuffer(gl, GL2GL3.GL_RGBA, _width / 2, _height / 2, 0, GL2GL3.GL_RGBA,
            GL2GL3.GL_UNSIGNED_BYTE, GL2GL3.GL_TEXTURE_MIN_FILTER, GL2GL3.GL_TEXTURE_MIN_FILTER, GL2GL3.GL_REPEAT, null);
    int frameBufferId = GLHelper.makeFrameBuffer(gl, _frameBufferTextureId, _width / 2, _height / 2);
    return frameBufferId;
}

public static int makeTextureBuffer(GL2GL3 gl, int glEnumInternalFormat, int width, int height, int border,
        int glEnumPixelFormat, int glEnumPixelType, int glEnumMinFilter, int glEnumMagFilter, int glEnumWrapMode,
        File textureFile) {
    ByteBuffer textureDataBuffer = null;
    if (textureFile != null) {
        String filePath = textureFile.getPath();
        String extension = filePath.substring(filePath.lastIndexOf('.') + 1, filePath.length());
        TextureData textureData = null;
        try {
            textureData = TextureIO.newTextureData(gl.getGLProfile(), textureFile, false, extension);
        } catch (IOException e) {
            throw new RuntimeException("Error reading texture");
        }
        textureDataBuffer = getProperlyFormattedBuffer(textureData);
    }
    IntBuffer texture = IntBuffer.allocate(1);
    gl.glGenTextures(1, texture);
    gl.glBindTexture(GL2GL3.GL_TEXTURE_2D, texture.get(0));
    gl.glTexParameteri(GL2GL3.GL_TEXTURE_2D, GL2GL3.GL_TEXTURE_MIN_FILTER, glEnumMinFilter);
    gl.glTexParameteri(GL2GL3.GL_TEXTURE_2D, GL2GL3.GL_TEXTURE_MAG_FILTER, glEnumMagFilter);
    gl.glTexParameteri(GL2GL3.GL_TEXTURE_2D, GL2GL3.GL_TEXTURE_WRAP_S, glEnumWrapMode);
    gl.glTexParameteri(GL2GL3.GL_TEXTURE_2D, GL2GL3.GL_TEXTURE_WRAP_T, glEnumWrapMode);
    gl.glTexImage2D(GL2GL3.GL_TEXTURE_2D, 0, glEnumInternalFormat, width, height, border, glEnumPixelFormat, glEnumPixelType,
            textureDataBuffer);
    gl.glBindTexture(GL2GL3.GL_TEXTURE_2D, 0);
    return texture.get(0);
}

public static int makeFrameBuffer(GL2GL3 gl, int textureBufferId, int width, int height) {
    IntBuffer frameBuffer = IntBuffer.allocate(1);
    gl.glGenFramebuffers(1, frameBuffer);
    gl.glBindFramebuffer(GL2GL3.GL_FRAMEBUFFER, frameBuffer.get(0));
    gl.glFramebufferTexture2D(GL2GL3.GL_FRAMEBUFFER, GL2GL3.GL_COLOR_ATTACHMENT0, GL2GL3.GL_TEXTURE_2D, textureBufferId, 0);
    verifyFrameBuffer(gl);
    gl.glBindFramebuffer(GL2GL3.GL_FRAMEBUFFER, 0);
    return frameBuffer.get(0);
}

private void drawTextureQuad(GL2GL3 gl) {
    _glowShader.bind(gl);
    int textureLocation = _glowShader.getUniformFields().getIlluminationTextureLocation();
    gl.glUniform1i(textureLocation, 0);
    gl.glActiveTexture(GL2GL3.GL_TEXTURE0);
    gl.glBindTexture(GL2GL3.GL_TEXTURE_2D, _frameBufferTextureId);

    int vertexLocation = _glowShader.getAttributeFields().getVertexLocation();
    gl.glBindBuffer(GL2GL3.GL_ARRAY_BUFFER, _textureQuadId);
    gl.glVertexAttribPointer(vertexLocation, 3, GL2GL3.GL_FLOAT, false, 0, 0);
    gl.glEnableVertexAttribArray(vertexLocation);

    int textureCoordLocation = _glowShader.getAttributeFields().getVertexTextureCoordinateLocation();
    gl.glBindBuffer(GL2GL3.GL_ARRAY_BUFFER, _textureQuadCoordsId);
    gl.glVertexAttribPointer(textureCoordLocation, 2, GL2GL3.GL_FLOAT, false, 0, 0);
    gl.glEnableVertexAttribArray(textureCoordLocation);

    gl.glDrawArrays(GL2GL3.GL_TRIANGLE_FAN, 0, 4);
    _glowShader.unbind(gl);
}

In my render loop, I am doing the following:

_glowShader.bind(gl);// bind my Shader object.
gl.glUniformMatrix4fv(_glowShader.getUniformFields().getProjectionMatrixLocation(), 1, true, _projectionMatrix.getBuffer());
gl.glUniformMatrix4fv(_glowShader.getUniformFields().getModelViewMatrixLocation(), 1, true, _modelViewMat.getBuffer());
gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, _framebufferId);
gl.glDrawBuffers(1, _frameBufferAttachmentss); //contains GL_COLOR_ATTACHMENT0
gl.glViewport(0, 0, _width / 2, _height / 2); // same size as texture
_spaceship.draw(gl, _glowShader);// draw method in my ModelObject class
gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, 0);
_glowShader.unbind(gl);

drawTextureQuad(gl);

When I run this, my quad is drawn as it should, but the texture is all black. When I comment out any framebuffer bindings in my render loop, the model is rendered as it should, so I know that there is nothing wrong with my shader code. When I replace _frameBufferTextureId with another texture loaded from a file, that texture is properly drawn, so I know my texture coordinates are working and, again, my shader code is correct. Whenever I bind my frame buffer though, I don't get anything I expect. I'm also verifying my framebuffer and it is GL_FRAMEBUFFER_COMPLETE.

I've read countless tutorials and posts here on stackoverflow, but I can't for the life of me figure out what I'm doing wrong. Any help would be great! Thanks.

It probably doesn't matter but, in createFrameBuffer, it appears you pass the minification filter twice instead of the magnification filter. — Nicolas Lefebvre
I LOVE YOU!!! Sorry if that made you uncomfortable, but that was the source of my problem! I actually should have never been passing in GL_TEXTURE_MIN_FILTER as those are the targets in the glTexParameteri() method, not the arguments. I changed it to be GL_LINEAR for the GL_TEXTURE_MIN_FILTER and GL_TEXTURE_MAX_FILTER targets, and it works perfectly! :D — Wagan8r
Ah, I don't know jogl so I couldn't figure out how the filters worked, I thought maybe they were set globally and assigned to GL_TEXTURE_MIN_FILTER. Makes a lot more sense with your fix ;) — Nicolas Lefebvre

Wagan8r Wagan8r · Accepted Answer · 2011-06-02T17:28:30

As Bethor pointed out, I was passing in GL_TEXTURE_MIN_FILTER twice to my makeTextureBuffer method. This was resolving to the glTexParameteri() calls of:

gl.glTexParameteri(GL2GL3.GL_TEXTURE_2D, GL2GL3.GL_TEXTURE_MIN_FILTER, GL2GL2.GL_TEXTURE_MIN_FILTER);
gl.glTexParameteri(GL2GL3.GL_TEXTURE_2D, GL2GL3.GL_TEXTURE_MAG_FILTER, GL2GL2.GL_TEXTURE_MIN_FILTER);

which of course, makes no sense. Changing my calls to pass in GL_LINEAR fixed everything.

OpenGL Framebuffer Render to Texture not Working

1 Answers