Texture with alpha overlay

Troubleshooting graphics
1

Hello,



I have been searching for a method, which allows me to pass 2 textures to a material; a base texture and a overlay. The overlay should have a alpha channel, trough which the base texture is visible. My search led me to a 6 year old topic, with no straight answers.

My guess is that I have to make or customize a shader, but since I have no experience with shaders I’m looking for a easier and/or existing method.



I could load the 2 textures and merge them into 1 texture before passing it to the material, but I would like the overlay to be random (will be using it for dirt and wear). So if I generate all those combinations, I will have a lot of textures to cache.



Could someone push me into the right direction?

Thanks!

2

Look at Terrain.frag to see how to do “texture splatting”. For a more advanced version that handles lighting, look at TerrainLighting.frag (and the corresponding ,j3md files)

2 Likes
3

Thanks, I’ve been able to build something from that.



If other people want to do this, this is how I did it;



I used the ‘Lighting’ shader as a base. In the .j3md file, add this line below the DiffuseMap definition (#54).

Texture2D DiffuseOverlay



In the .j3md file, add this line under ‘Technique{ Defines {… } }’ (#162)

DIFFUSEOVERLAY : DiffuseOverlay



In the .frag file, add these lines below the DIFFUSEMAP definition (#29)

#ifdef DIFFUSEOVERLAY

uniform sampler2D m_DiffuseOverlay;

#endif



And finally, in the .frag file, add these lines below “vec4 diffuseColor = texture2D(m_DiffuseMap, newTexCoord);” (#170)

#ifdef DIFFUSEOVERLAY

vec4 alphaBlend = texture2D( m_DiffuseOverlay, texCoord.xy );

vec4 diffuseOverlay = texture2D(m_DiffuseOverlay, newTexCoord);

diffuseColor = mix( diffuseColor, diffuseOverlay, alphaBlend.a );

#endif





When creating a material, you can just pass the overlay texture like this

[java]material.setTexture(“DiffuseOverlay”, texture);[/java]

4 Likes
4

Very nicely articulated!