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A few questions about POM/LOD/shadow maps

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Hello all Gamedevers, I`d like to ask few things that are unclear to me but important. 1)first thing is about performance of POM and similar techniques. Is there any difference in performance(I can`t try it on my own becouse I don`t have access to my computer and won`t have it for pretty long time) if I`ve got one big texture over whole screen, or if I`ve got ten(or fifty) smaller faces with different textures, over whole screen too. There should be only slight difference becouse most of computing in POM is done in pixel shader. Is that correct? 2)second thing is that if it is worthy to use LOD textures in certain situation. for example if I`ve got a long path covered only with one texture(maybe pavement) repeated. I have to have that hi-res texture loaded in video memory becouse its near, but its used again in great distance. my question is if the performance is the same if I use high resolution texture to cover whole path without any performance hit. 3)third thing is quite simple. how do I do shadow map for a point light? I`ve got two ideas. use single texture and set field of view to 360 degrees, or use cube texture. I like more single texture becouse its easier to implement and I guess its faster too(I haven`t used cube textures before), but I don`t know if quality of shadows would be bearable to watch:) 4)now again POM and similar again. if I`ve got nearly static light, for example torch and actual light point in it would slightly move to give illusion of fire, is it good idea to keep offsets that are computed when computing if a texel is in light or in shadow(for self shadowing)? I mean, if light point moves only slightly, offset value changes only slightly too. so if I know offset value of the last frame, in shader I can try to search for new offset near old offset, and if it isnt there I can do whole proccess of searching for offset again. that might save most of itterations. thats just an idea, I havent implemented POM before. I also dont know how fast is saving offsets to texture(and how to do it) and reading them next frame. 5)and finally last thing. I haven`t though about it much yet, but is there any simple way how to combine shadow maps and self-shadowing POM-like techniques and save as much performance as possible? Alright, that`s all for now. I guess I`ll come with more questions later becouse I`m designing my first engine(whoa!). tnx in advance!

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"I`ve got two ideas. use single texture and set field of view to 360 degrees, or use cube texture"

You cant use a single texture, because 360 degrees is impossible.. you get just big blurs. Because of the resolution, the shadow map algorithm fails.

You can get away with 2 textures and 2 views if you use some kind of dual parabola mapping, but this requires relatively high tesselation.

Normally you must use a cubemap( or six unrolled textures) and six rendered views.

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Original post by Matt Aufderheide
"I`ve got two ideas. use single texture and set field of view to 360 degrees, or use cube texture"

You cant use a single texture, because 360 degrees is impossible.. you get just big blurs. Because of the resolution, the shadow map algorithm fails.

You can get away with 2 textures and 2 views if you use some kind of dual parabola mapping, but this requires relatively high tesselation.

Normally you must use a cubemap( or six unrolled textures) and six rendered views.


yeah I though I would have to go for cubemap. thank you for explanation

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