Drawing a filled Cube

1

Hi all ,

I am new to game dev/3d dev and this is just a visualization project for something else I am working on.

What I want to do:
I am looking to create a transparent cube in which some of the pixels inside the cube can be different colors. The color and the location of the pixel should be changeable in the update cycle.

What I have tried so far:
I created a .fbx cube in blender and exported it out and rendering the cube with the following effect.fx

What is wrong
I only get a solid colored cube.

I am not sure what I am doing wrong :frowning:

Any help would be amazing! thanks !

effect.fx

Texture3D SpriteTexture;

sampler3D SpriteTextureSampler = sampler_state
{
	Texture = <SpriteTexture>;
};


struct InstancingVSinput
{
	float4 Position : POSITION0;
	float3 TexCoord : TEXCOORD0;
};

struct InstancingVSoutput
{
	float4 Position : POSITION0;
	float3 TexCoord : TEXCOORD0;
};
float4 InstancingPS(InstancingVSoutput input) : COLOR0
{
	float4 caluclatedColor = tex3D(SpriteTextureSampler, input.TexCoord);
	return caluclatedColor;
}
matrix WorldMatrix;

InstancingVSoutput MainVS(in InstancingVSinput input)
{
	InstancingVSoutput output = (InstancingVSoutput)0;
	output.Position = mul(input.Position, WorldMatrix);
	output.TexCoord = input.TexCoord;
	return output;
}
technique Instancing
{
	pass P0
	{
		VertexShader = compile VS_SHADERMODEL MainVS();
		PixelShader = compile PS_SHADERMODEL InstancingPS();
	}
};

Loading Model and Effect

        camera = new Camera3d(GraphicsDevice.Viewport, GraphicsDevice.Viewport.AspectRatio);
        texture = new Texture3D(GraphicsDevice, 50, 50,50,false,SurfaceFormat.Color);

        var d = new Color[50 * 50 * 50];
        for (int k = 0; k < d.Length; k++)
        {
            d[k] = new Color(33, 33, 33,100);
        }
        d[50] = new Color(255, 255, 255, 100);
        texture.SetData(d);

        effect = Content.Load<Effect>("Effect");

        effect .Parameters["SpriteTexture"].SetValue(texture);
        mdl.Meshes[0].MeshParts[0].Effect = effect;

Draw Code

        foreach(ModelMesh mesh in mdl.Meshes)
        {
            foreach (EffectPass pass in effect.CurrentTechnique.
                 Passes)
            {
                pass.Apply();
                mesh.Draw();
            }
        }