When checking for errors, I get [EDIT:] 1282 (“invalid operation”). I take this to mean that the OpenGL is still using OpenGL 2 for glTexImage2D, and so the call is failing. OpenGL errors are not that complex to understand. GL_INVALID_ENUM/VALUE are thrown when you pass something an enum or value that is unexpected, unsupported, or … Read more
Perhaps the following illustration showing the relationship between the various spaces will help: Depending if you’re using the fixed-function pipeline (you are if you call glMatrixMode(), for example), or using shaders, the operations are identical – it’s just a matter of whether you code them directly in a shader, or the OpenGL pipeline aids in … Read more
Now, my question is for the elbow. Why is there a translation forward on the x-axis both before and after the rotate? If you want to imagine how the matrix operations change the model, then you need to “read” the operations in the reverse order. This is, because the current matrix of the matrix stack … Read more
If you have to following rectangle, where the red cross is the center of the world and you want to rotate it around the green pivot then you’ve to do the following steps: Translate the rectangle in that way that way, that the pivot is on the origin of the world. This is a translation … Read more
Yes, the OpenGL Extension Wrangler Library (GLEW) is a painless way to use OpenGL extensions on Windows. Here’s how to get started on it: Identify the OpenGL extension and the extension APIs you wish to use. OpenGL extensions are listed in the OpenGL Extension Registry. Check if your graphic card supports the extensions you wish … Read more
I’d like to extent on BDL’s answer. It is not only about the perspective interpolation. It is also about the clipping. The space the value gl_Position is supposed to be provided in is called clip space, and this is before the division by w. The (default) clip volume of OpenGL is defined in clip space … Read more
VAOs act similarly to VBOs and textures with regard to how they are bound. Having a single VAO bound for the entire length of your program will yield no performance benefits because you might as well just be rendering without VAOs at all. In fact it may be slower depending on how the implementation intercepts … Read more
You can’t easily communicate back to the CPU from within GLSL. Using glslDevil or other tools is your best bet. A printf would require trying to get back to the CPU from the GPU running the GLSL code. Instead, you can try pushing ahead to the display. Instead of trying to output text, output something … Read more
Rendering outlines, unless you render only a dozen characters total, remains a “no go” due to the number of vertices needed per character to approximate curvature. Though there have been approaches to evaluate bezier curves in the pixel shader instead, these suffer from not being easily antialiased, which is trivial using a distance-map-textured quad, and … Read more
OpenGL (and D3D. And Metal. And Mantle. And Vulkan) doesn’t support this because hardware doesn’t support this. Hardware doesn’t support this because, for the vast majority of mesh data, this would not help. This is primarily useful for meshes that are predominantly not smooth (vertices sharing positions but not normals and so forth). And most … Read more