Category Archives: opengl

Shadow Maps on Omnidirectional Lights

Theoretically, using six shadow mapped spot lights to piece up a shadow casting point light is not a big deal. Especially if the light geometry calculation for deferred lighting is correct. Well, in my engine, it was not the case. 🙂

There was a hidden calculation error that resulted in a frustum with incorrect corner points that made it bigger than desired. This error caused no problem so far because projected mask texture on spotlights and “discard” codes in fragment shader prevented the extra pixels from being seen. But once I have used spot lights with no mask to render point light, the result was erroneous. It looked so strange and mysterious that it took few hours to find the root of the problem.

Finally, the shadows on point light are working now, and I proudly present some screenshots here.

Shadow map on omnilight. Shadow map on omnilight. Shadow map on omnilight. Shadow map on omnilight.

Dynamic Daylight

I have made dynamic sunlight and shadow support wired to the UI, so the sun position can be controlled interactively. The engine calculates the sun position by using azimuth and elevation as parameters. Sun and fog color is adjusted according to the elevation by using a color gradient generated with GIMP. The result can be seen here:

Through the Valley of Cascaded Shadows and Depth

After some struggling with frustum and light projection matrix calculation, CSM is finally working in the engine. There are four splits, parallel light projection and dynamic bounding frustum calculation. The technique is basically the same as described in the NVidia’s article.

There is still some annoying bug with frustum culling in the shadow map render code, thus, the shadows are leaking sometimes. But performs quite good after all.

Here are some pictures of the results.

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Porting Back to Linux II.

This post is the second part of another I posted earlier.

The detection of uninitialized class members is one of  of my recurring problems with C++. The language standard does not guarantee anything about member variables so I should initialize them myself. Unfortunately, VC++ compiler does not warn me if I forget to initialize a class member variable, even if I set the highest warning level. GCC detects this kind of sloppiness and reports them to me keenly, making great improvements in code quality. Furthermore, GCC goes one step beyond and warns me if the initialization order differs from the declaration order (see Effective C++ about this).
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