I changed the code to use effect_load(), but it makes no difference, the decal is still one big black square:

function shader_road()
{
my.material = road_shader;

//if(lightmap_level == 1){road_shader.effect = "multitex4_ps1_0sha.fx";}
//if(lightmap_level != 1){road_shader.effect = "multitex4_ps1_0ans.fx";}

effect_load(road_shader,"multitex4_ps1_0sha.fx");

road_shader.ambient_red = road_ambient.x;
road_shader.ambient_blue = road_ambient.y;
road_shader.ambient_green = road_ambient.z;

road_shader.diffuse_red = road_diffuse.x;
road_shader.diffuse_blue = road_diffuse.y;
road_shader.diffuse_green = road_diffuse.z;
}

I'm not sure if I understand the problem right: Your code assigns mat_model to the decal, but your other functions are doing something with a material named road_shader. So when does your decal become black - when your road gets assigned the other material?

Yeah, I'm sorry I wasn't very clear. The material, road_shader, is applied to the ground only. The decal is black when the road_shader is applied to the ground, and mat_model is applied to the decal. Although, if I apply mat_model to both the road shader and the decal, it works.

Ah, ok. Can you send the level to the support? We'll look into that problem.

Sure, I might not be able to send it until Monday though.

I sent it your email address JCL.

Thanks. We got it and will look into it.