Question

I’m writing a game in Visual Studio 2010, using the XNA 4.0 framework. I have a 3D terrain model generated from a height map. What I’m trying to accomplish is to tint this model in a given radius around a certain point, the end goal being to display to the player the radius in which a unit can move in a given turn. The method I’m using to draw the model at the moment is this:

void DrawModel(Model model, Matrix worldMatrix)
    {
        Matrix[] boneTransforms = new Matrix[model.Bones.Count];
        model.CopyAbsoluteBoneTransformsTo(boneTransforms);

        foreach (ModelMesh mesh in model.Meshes)
        {
            foreach (BasicEffect effect in mesh.Effects)
            {
                effect.World = boneTransforms[mesh.ParentBone.Index] * worldMatrix;
                effect.View = camera.viewMatrix;
                effect.Projection = camera.projectionMatrix;


                effect.EnableDefaultLighting();
                effect.EmissiveColor = Color.Green.ToVector3();
                effect.PreferPerPixelLighting = true;

                // Set the fog to match the black background color
                effect.FogEnabled = true;
                effect.FogColor = Color.CornflowerBlue.ToVector3();
                effect.FogStart = 1000;
                effect.FogEnd = 3200;
            }

            mesh.Draw();
        }
    }

Also, in case it’s relevant, I followed this tutorial http://create.msdn.com/en-US/education/catalog/sample/collision_3d_heightmap to create my heightmap and terrain.

Thanks in advance for any help!

Answer 1

You can use a shader to achieve that…

you only would need to pass as argument the world position of the center and the radius,
and let the pixel shader receive the pixel world position interpolated from the vertex shader as a texture coord…
then only have to check the distance of the pixel position to the center and tint it with a color if the pixel position is in range…