Hello,
So basically I’ve been tearing my hair out getting some really basic lighting in 3D to work. I don’t think this is specific to Monogame, as I remember having similar issues when I tried this an old OpenGL project.
In a nutshell, I’m having (I think) issues with translating my normals on models.
The Image below shows what I mean. I have a light positioned at the camera. The cube in the middle is rotating. Looks mostly fine.
The other cube is orbiting the central one and you can see the front face is dark where it should be lit.
I’ve been tearing my hair out trying to work out why this is happening. Its just a simple shader with ambient and diffuse lighting, no specular.
I’m using the Monogame Crossplatform template. My drawing code is as follows:
public void Draw(GraphicsDevice g, Effect effect)
{
effect.Parameters["View"].SetValue(mView);
effect.Parameters["Projection"].SetValue(mProjection);
Matrix world = Matrix.Identity;
world *= Matrix.CreateFromQuaternion(mRotation);
world *= Matrix.CreateScale(mScale);
world *= Matrix.CreateTranslation(mPosition);
effect.Parameters["World"].SetValue(world);
effect.Parameters["NormalMat"].SetValue(Matrix.Transpose(Matrix.Invert(world)));
effect.Parameters["IsLightSource"].SetValue(mIsLightSource);
g.SetVertexBuffer(mShape);
foreach (EffectPass pass in effect.CurrentTechnique.Passes)
{
pass.Apply();
g.DrawPrimitives(PrimitiveType.TriangleList, 0, mShape.VertexCount);
}
}
The shader code I adapted from Riener’s tutorial:
float4x4 World;
float4x4 View;
float4x4 Projection;
float3x3 NormalMat; //if a 4x4 only uses 3x3 Monogame will error due to HLSL optimizer removing final row
float3 LightSourcePosition;
bool IsLightSource;
struct VertexShaderInput
{
float4 Position : POSITION;
float4 Color : COLOR0;
float3 Normal : NORMAL0;
};
struct VertexShaderOutput
{
float4 Position : POSITION0; //cannot be passed pixel shader in ps_2_0
float4 PosOut : TEXCOORD1; //Label as texture to pass position to pixel shader.
float4 Color : COLOR0;
float3 Normal : TEXCOORD0;
};
VertexShaderOutput VertexShaderFunction(VertexShaderInput input)
{
VertexShaderOutput output;
float4 worldPosition = mul(input.Position, World);
float4 viewPosition = mul(worldPosition, View);
output.Position = mul(viewPosition, Projection);
output.PosOut = output.Position;
output.Color = input.Color;
output.Normal = normalize(mul(input.Normal, NormalMat));
return output;
}
float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0
{
float3 ambientColor = input.Color.xyz * 0.1f;
if (IsLightSource == true)
{
return input.Color;
}
float3 lightDirection = normalize(LightSourcePosition - input.PosOut.xyz);
float diffuseIntensity = max(dot(input.Normal, lightDirection), 0);
float3 diffuseColor = input.Color.xyz * diffuseIntensity;
return float4(ambientColor + diffuseColor,1);
}
technique Ambient
{
pass Pass1
{
VertexShader = compile vs_2_0 VertexShaderFunction();
PixelShader = compile ps_2_0 PixelShaderFunction();
}
}
As I understand it with normals, you multiply them by a transposed, inverse of the world matrix to remove the scaling. My understanding is sketchy (as the results show) so any insight into what I’m doing wrong would be great.
This isn’t an issue with Monogame (I don’t think, but just in case I’m running Win7x64 with a gtx950).
Any help or replies are very much appreciated.
(As an aside): I made an account with my email previously but it won’t let me sign in, will only let me make a new account, hence this new account. Any ideas on that would be appreciated too.
