I'm trying to understand how framebuffers work. In order to achieve that, I want to draw a very basic triangle to a framebuffer texture and then draw the resulting texture to a quad on the default framebuffer.
However, I only get a fraction of the triangle like below. LE: The triangle's coordinates should be (1) -0.5f, -0.5f, 0 (2) 0.5f, -0.5f, 0 (3) 0, 0.5f, 0
Here's the code to render:
@Override
public void onDrawFrame(GL10 gl) {
renderNormalStuff();
renderFramebufferTexture();
}
protected void renderNormalStuff() {
GLES20.glViewport(0, 0, texWidth, texHeight);
GLUtils.updateProjectionMatrix(mProjectionMatrix, texWidth, texHeight);
GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, fbo[0]);
GLES20.glUseProgram(mProgram);
GLES20.glClearColor(.5f, .5f, .5f, 1);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
Matrix.setIdentityM(mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(u_MVPMatrix, 1, false, mMVPMatrix, 0);
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[0]);
GLES20.glVertexAttribPointer(a_Position, 3, GLES20.GL_FLOAT, false, 12, 0);
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[1]);
GLES20.glVertexAttribPointer(a_Color, 4, GLES20.GL_FLOAT, false, 16, 0);
GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, ibo[0]);
GLES20.glDrawElements(GLES20.GL_TRIANGLES, indexBuffer.capacity(), GLES20.GL_UNSIGNED_BYTE, 0);
GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);
GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, 0);
GLES20.glUseProgram(0);
}
private void renderFramebufferTexture() {
GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
GLES20.glUseProgram(fboProgram);
GLES20.glClearColor(.0f, .5f, .25f, 1);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
GLES20.glViewport(0, 0, width, height);
GLUtils.updateProjectionMatrix(mProjectionMatrix, width, height);
Matrix.setIdentityM(mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(fbo_u_MVPMatrix, 1, false, mMVPMatrix, 0);
//draw the texture
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture[0]);
GLES20.glUniform1i(fbo_u_Texture, 0);
GLUtils.sendBufferData(fbo_a_Position, 3, quadPositionBuffer);
GLUtils.sendBufferData(fbo_a_TexCoordinate, 2, quadTexCoordinate);
GLES20.glDrawElements(GLES20.GL_TRIANGLES, quadIndexBuffer.capacity(), GLES20.GL_UNSIGNED_BYTE, quadIndexBuffer);
GLES20.glUseProgram(0);
}
