Atlas and Sunlight

Hello everyone. I've recently been working on a tgedaynight port for Josh's MMO Kit on TGEA (a TGE version of his code can be found in the resource section here or in his Kit). One of the issues of course with Atlas is that it doesn't respond to sunlight. I found it was very easy to get it working with sunlight though, so maybe this will be of useful to some of you out there. I also have one minor issue that is happening and will mention that here. This problem only happens if you are changing the sunlights value over time.

To get in basic functionality all you need to edit in code is your AtlasClipMapBlenderCache.cpp or AtlasClipMapUniqueCache.cpp to pass the sunlight to your shader.

Before the DrawIndexedPrimitive calls you want to add something like this:

F32 sunlightcolor = tgeDNCurrentColor.x; 
GFX->setPixelShaderConstF (PC_USERDEF1, (float*)&sunlightcolor, 1);

Note in the above example it's using tgeDNCurrentColor's red value and assuming this is uniform for your green and blue. If you aren't using the daynight code and you wanted to get suns ambient light or sunlight in there you would want to pull the current color from there (sun->ambient or something similar).

You'd then just have to edit the shaders (atlasblenderps20p.hlsl for example for the pixel shader 2.0 blender terrain shader) so that they multiply the suns color by the terrain color. example below from atlasblenderps20p.hlsl:

Fragout main(v2f IN, 
   uniform sampler2D    opacity  : register(S0), 
   uniform sampler2D    lightMap : register(S1), 
   uniform sampler2D    tex1     : register(S2), 
   uniform sampler2D    tex2     : register(S3), 
   uniform sampler2D    tex3     : register(S4), 
   uniform sampler2D    tex4     : register(S5),  // note added a comma
    uniform float sun : register (C6) // <-- this is new
) 
{ 
   Fragout OUT; 

   // Get colors 
   float4 o  = tex2D(opacity,  IN.tex); 
   float4 t1 = tex2D(tex1,     IN.tex1); 
   float4 t2 = tex2D(tex2,     IN.tex2); 
   float4 t3 = tex2D(tex3,     IN.tex3); 
   float4 t4 = tex2D(tex4,     IN.tex4); 
   float4 lm = tex2D(lightMap, IN.lmTex); 

   // Blend 
   OUT.col = lm * (o.r * t1 + o.g * t2 + o.b * t3 + o.a * t4) * sun;  // note: this is changed
    
   return OUT; 
}

That will give you some simple lighting in your scene. If your sunlight is changing over time though (as in the tgedaynight code) then you will run into a problem over time, in that your atlas textures will become borked, as some do not update properly to the new lighting. With subtle changes this doesn't become evident for a while, but if you are going from like 3am to noon, you will wind up with rather nasty black blotches.

I'm still trying to find a real fix for this, but currently I have found a workaround for it. When it ticks to a new hour of gametime (in my case every 3 minutes) I had it reset the textures with this line of code:

GFX->resurrectTextureManager();

This works, but it does cause the graphics to hitch momentarily. It's pretty fast on my system (under 100 ms) but I have a pretty fast system here. On slower systems it might hitch much longer. For now that is a reasonable workaround, I'd like to find a better way of handling it. I have experimented with only resurrecting the atlas textures but had problems getting that to function properly (never worked). If anyone has any ideas feel free to share them.

A shot of this in action can be seen here: http://www.therepopulation.com/daynighttest.jpg