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Lightmaps and Defered Shading ?

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Hi all Im starting to learn concepts about Deferred Shading. I know that there is a 'first step' calculating something called G-Buffer that is the 'base' data to play later, data like color, normal, depth and more. Then, with this data we can step into light calculating step 'adding' every light making use of stencil buffers to optimize, etc. But how about lightmaps ? is there a way to use them in this kind of render technique ? Im thinking that graphic card can only ouput 4 RT at a time, so if i need a 5th RT with lightmap information i must do another pass to all geometry. Im thinking i miss something. Thanks for your time :) LLORENS

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Well most games with differed renderers dont use lightmaps anyway...why not use sahdow maps?

However there is no reason you should use more than 4 render targets anyway...

one for diffuse color
one for normal/depth (you can reconstruct position from depth..just store depth in alpha)
one for lightmaps
anotehr for anything else...

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Just initialize the light accumulation buffer with the data from the light maps. It's also a good place to store your emissive data.

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Hi all

Thx for fast response.

One question: When you are in the light stage on a defered shading, how you can initialize your light acumulation buffer with lightmap information without send another time all the geometry to render ?

Another question that arise in my head: Do you initialize your acumulation light buffer in a defered render technique? I ask this because in my forward render technique i use an interpolation between lightmap information and dynamic light influence on the pixel. Ie: if you have a 0.3 dinamic light difuse factor, then i interpolate 30% of color provided by dinamci light, and 70% of color provided by lightmap light.

Do you think that lightmaps will not be used in future ? i know that if you put a global direct light and some local omni lights in a defered shading render, you can reach a very beautifull render, but, if you manage lightmaps in a right way, you can acomplish the same render with less dynamic lights.

Thanks for yout time :)

LLORENS

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