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Environment maps in dark environments


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#1 Ashaman73   Crossbones+   -  Reputation: 7101

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Posted 14 January 2013 - 12:46 AM

I'm struggeling with environment maps in dark environments and want to know if there might be some tricks to reduce its artifacts.

 

The issue is, that in dark environments surfaces will not receive any standard diffuse/specular light, only the light source indepedent environment map will light them up, making it clearly visible, especially in HDR rendering (low key value). Using proper light probes will limit the effect, but my game is often very dark and very dynamic when it comes down to light sources and level topology.

 

This effect can be observed in other games too, e.g. L4D2 where certain guns uses env-maps in dark areas.

 

Any ideas ?



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#2 MJP   Moderators   -  Reputation: 10828

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Posted 14 January 2013 - 05:32 PM

One thing some games do is they will "normalize" their reflection probes by dividing all texels by the intensity of the brightest texel. Then at run time they will multiply the reflection map value by the intensity of the baked diffuse lighting (usually either light maps or SH environment probes). This helps the probes "fit in" better with varying lighting conditions, especially if your probes are sparse.

You can also potentially make your reflections a lot better in all conditions by pre-baking some AO. This can be especially useful if you're using a fresnel term, since it tends to produce a rim-lighting-esque effect on meshes if you don't apply any visibility to the sampled reflections.


Edited by MJP, 14 January 2013 - 05:34 PM.


#3 Ashaman73   Crossbones+   -  Reputation: 7101

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Posted 15 January 2013 - 12:52 AM

Then at run time they will multiply the reflection map value by the intensity of the baked diffuse lighting (usually either light maps or SH environment probes).

I've no light maps or similar available, but I thought about using the light intensity to adjust the power of  the env-map. The disadvantage is, that I need to apply it after the lighting passes are completed, this is an additional fullscreen pass + reading of the material buffer (stencil buffer is of no use here due to the material management).

 

You can also potentially make your reflections a lot better in all conditions by pre-baking some AO. This can be especially useful if you're using a fresnel term, since it tends to produce a rim-lighting-esque effect on meshes if you don't apply any visibility to the sampled reflections.

I often use pre-baked AO to reduce the env-map effect in darker areas of the mesh, fresnel is although installed, still HDR and env-maps are tricky and hard to tweak (in bright parts of the map you almost don't see the effect, in dark partsit is almost glowing).

 

I will test out your first sugguestion, thx for the feedback.



#4 Ashaman73   Crossbones+   -  Reputation: 7101

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Posted 18 January 2013 - 10:16 AM

I've finally found a solution which works quite good for me. I've posted my result in my journal over here.

 

Here's a screenshot of the final result:

gnoblins_env_comparision.png






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