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POTrying to implement Render to Texture
 

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  1. POTrying to implement Render to Texture
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    <p>I'm having trouble implementing render to texture with OpenGL 3.</p> <p>My issue is that after rendering to the frame buffer, it appears the rendered object becomes deformed, which may imply a bad transformation has occurred somewhere. Which doesn't make sense as the object renders fine when <strong>not</strong> using my frame buffer (see bottom of post).</p> <p><strong>The current result is such:</strong></p> <p><a href="http://k.minus.com/jZVgUuLYRtapv.jpg" rel="nofollow noreferrer">Current result http://k.minus.com/jZVgUuLYRtapv.jpg</a></p> <p><strong>And the expected result was this (or something similar, this has just been GIMP'd):</strong> <a href="http://k.minus.com/jA5rLM8lmXQYL.jpg" rel="nofollow noreferrer">Expected http://k.minus.com/jA5rLM8lmXQYL.jpg</a></p> <p>It therefore implies that I'm doing something wrong in my frame buffer set up code, or elsewhere. But I can't see what.</p> <hr> <p>The FBO is set up through the following function:</p> <pre><code>unsigned int fbo_id; unsigned int depth_buffer; int m_FBOWidth, m_FBOHeight; unsigned int m_TextureID; void initFBO() { m_FBOWidth = screen_width; m_FBOHeight = screen_height; glGenRenderbuffers(1, &amp;depth_buffer); glBindRenderbuffer(GL_RENDERBUFFER, depth_buffer); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, m_FBOWidth, m_FBOHeight); glGenTextures(1, &amp;m_TextureID); glBindTexture(GL_TEXTURE_2D, m_TextureID); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, m_FBOWidth, m_FBOHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0); glBindTexture(GL_TEXTURE_2D, 0); glGenFramebuffers(1, &amp;fbo_id); glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo_id); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_buffer); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_TextureID, 0); assert(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE); glBindFramebuffer(GL_FRAMEBUFFER, 0); } </code></pre> <p>Here is my drawing box code, which just takes a transformation matrix and calls the appropriate functions. The current values of P is a projection matrix, and an identity matrix for the view matrix (V).</p> <pre><code>void drawBox(const Matrix4&amp; M) { const Matrix4 MVP = M * V * P; if (boundshader) { glUniformMatrix4fv((*boundshader)("MVP"), 1, GL_FALSE, &amp;MVP[0]); } glBindVertexArray(vaoID); glDrawElements(GL_TRIANGLES, sizeof(cube.polygon)/sizeof(cube.polygon[0]), GL_UNSIGNED_INT, 0); } void drawStaticBox() { Matrix4 M(1); translate(M, Vector3(0,0,-50)); drawBox(M); } void drawRotatingBox() { Matrix4 M(1); rotate(M, rotation(Vector3(1, 0, 0), rotation_x)); rotate(M, rotation(Vector3(0, 1, 0), rotation_y)); rotate(M, rotation(Vector3(0, 0, 1), rotation_z)); translate(M, Vector3(0,0,-50)); drawBox(M); } </code></pre> <p>And the display function called by GLUT.</p> <pre><code>void OnRender() { ///////////////////////////////////////// // Render to FBO glClearColor(0, 0, 0.2f,0); glBindFramebuffer(GL_FRAMEBUFFER, fbo_id); glViewport(0, 0, m_FBOWidth, m_FBOHeight); glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT); GL_CHECK_ERRORS colorshader.Use(); boundshader = &amp;colorshader; drawRotatingBox(); colorshader.UnUse(); ///////////////////////////////////////// // Render to Window glClearColor(0, 0, 0, 0); glBindFramebuffer(GL_FRAMEBUFFER, 0); glViewport(0, 0, screen_width, screen_height); glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT); GL_CHECK_ERRORS texshader.Use(); boundshader = &amp;texshader; glBindTexture(GL_TEXTURE_2D, m_TextureID); drawStaticBox(); texshader.UnUse(); // Swap le buffers glutSwapBuffers(); } </code></pre> <hr> <p>And... the obligatory texture shader code</p> <p><strong>vertex</strong></p> <pre><code>#version 330 in vec2 vUV; in vec3 vVertex; smooth out vec2 vTexCoord; uniform mat4 MVP; void main() { vTexCoord = vUV; gl_Position = MVP*vec4(vVertex,1); } </code></pre> <p><strong>fragment</strong></p> <pre><code>#version 330 smooth in vec2 vTexCoord; out vec4 vFragColor; uniform sampler2D textureMap; void main(void) { vFragColor = texture(textureMap, vTexCoord); } </code></pre> <hr> <p><strong>The following is what is rendered when not using the FBO logic:</strong> <a href="http://k.minus.com/jiP7kTOSLLvHk.jpg" rel="nofollow noreferrer">What is rendered to the FBO http://k.minus.com/jiP7kTOSLLvHk.jpg</a></p> <hr> <p>... Help?</p> <p>Any ideas on what I may be doing wrong? Further source available on request.</p>
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    1. COMaybe your rendered buffer is OK, but the texture coordinates of the cube displaying the rendered buffer on its faces are wrong.
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      1. POTrying to implement Render to Texture
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    2. CO@Neodelphi, as was the case at the cross-post I made at http://gamedev.stackexchange.com/questions/17554/trying-to-implement-render-to-texture. You're comment was correct. Thanks a heap. Best make your comment an answer.
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