True 3D Selection for RTS

Hi, thanks for your response. To be clear on what I want: http://answers.unity3d.com/questions/442581/how-to-draw-a-grid-over-parts-of-the-terrain.html

This is a similar question, although I dont want to draw a fixed sized grid but a rectangle which is specified by mouse input. The provided solutions mostly use a mesh which is overlayed on the terrain. As you correctly point out, this is a. more difficult and b. not as "beautiful".

$$anonymous$$odifying the terrain shader could be a good idea, but I'm quite new to shader program$$anonymous$$g. How would you modify that shader? I would need several inputs, such as mouse position and if the mouse button is clicked.

well, first you'll need to copy all the relevent files for the terrain shaders. Its not too complicated, but there are a few. First, there's three actual terrain shaders 1 - the first pass terrain shader that draws the first four textures 2 - the add pass shader, drawing each successive four textures 3 - a simple distant shader

And a couple of include files but the one you might need is TerrainSplatmapCommon.

So first, copy the relevent files...I guess just add pass and first pass, along with TerrainSplatmapCommon.

Then I'd edit the SplatmapFinalColor function in TerrainSplatmapCommon, using IN.tc_Control (that's the uv coordinates to the splatmap). You could edit it later in the process, to make it occur after lighting, fog, etc. You can always move when it occurs though...have a look at the finalcolor function in the unity docs.

Anyway, you'd have to pass the two positions defining the rectangle to the shader (Shader.SetGlobalFloat, or material.SetFloat), relative to the terrain position, scaled to the 0..1 range.

The shader code would be something like:

 fixed4 selectionColor; // rgb, a is blend amount. This'd be a property (add to shaders property blocks), for convenience. 
 float2 dragPosition0, dragPosition1; // x, z position. Not properties, only applied through code. There used to be a thing where unity wouldn't set the values through code if something is a property, not sure if its still the case. 
 
 void SplatmapFinalColor(Input IN, TERRAIN_SURFACE_OUTPUT o, inout fixed4 color)
 {
     <snip>
     
     float2 $$anonymous$$ = ...;
     float2 max = ...;
 
     if (IN.tc_Control.x < $$anonymous$$.x && ... etc)
     {
         // mix, because if you just added colour you might be adding it beyond the colour range
         color.rgb = color.rgb * (1.0 - selectionColor.a) + selectionColor.rgb * selectionColor.a;
     }
 }

Hope that's enough to get you going. Oh, and after I'd finished I'd rename the shaders (and change related stuff, which is the #include statements, and the menu path for each shader) so I could still use the unedited terrain shaders if I wanted.

It works!

Only problem I have is, that if i dont set the "selection color" value of the shader in each frame, the selection is not visible. Further, if i dont CHANGE the color in each frame, no selection is visible. This is the shader code:

 //FirstPass.shader:
 Properties {
         ......
         _SelectionColor("Selection Color", Color) = (1,1,1,1)
     }
 
 //SplatmapCOmmon.cginc:
 ....
 fixed4 _SelectionColor;
 ...
 void SplatmapFinalColor(Input IN, TERRAIN_SURFACE_OUTPUT o, inout fixed4 color)
 {
     ......
 
         float xBegin = $$anonymous$$(_$$anonymous$$ousePosStart.x, _$$anonymous$$ousePosEnd.x);
         float xEnd = max(_$$anonymous$$ousePosStart.x, _$$anonymous$$ousePosEnd.x);
         float yBegin = $$anonymous$$(_$$anonymous$$ousePosStart.y, _$$anonymous$$ousePosEnd.y);
         float yEnd = max(_$$anonymous$$ousePosStart.y, _$$anonymous$$ousePosEnd.y);
 
         if (IN.worldPos.x > xBegin && IN.worldPos.x < xEnd)
         {
             if (IN.worldPos.z > yBegin && IN.worldPos.z < yEnd)
             {
                 color.rgb = color.rgb * (1.0 - _SelectionColor.a) + _SelectionColor.rgb * _SelectionColor.a;
             }
         }
 }

Well, that's not something I've seen before, but my guess is _SelectionColor is being used by something else, globally. Or maybe something is assigning the terrain material per frame.