What is the simplest way to implement transparent objects in sharpdx? - graphics

Question

I am currently trying to implement semi-transparent polygons in sharpdx.
At the moment I am using GraphicsDevice and BasicEffect to draw my objects.
// Setup the vertices
game.GraphicsDevice.SetVertexBuffer(myModel.vertices);
game.GraphicsDevice.SetVertexInputLayout(myModel.inputLayout);
// Apply the basic effect technique and draw the object
basicEffect.CurrentTechnique.Passes[0].Apply();
game.GraphicsDevice.Draw(PrimitiveType.TriangleList, myModel.vertices.ElementCount);
This is working fine for normal objects, however I would like to make some of the objects partially transparent. I've set the alpha value of these object's colors to 50, however they are still being rendered as opaque. What do I need to do to achieve this effect?

Answer 1

Transparency in Sharpdx requires alpha blending value 0..1 for float colors. The comment Nico Schertler provided above solved the question and can be regarded as answer.
Without Alpha mode, there are two options, that you can use in the HLSL shader file
In the Pixel shader, use the clip() function, dependent on the input color. You could define your transparent black and not show any black triangles. Like so:
float4 PS( PS_IN input ) : SV_Target
{
clip(input.color[3] < 0.1f ? -1:1 );
return input.color;
}
ref: https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-clip
See the effect:
modify the Vertex Shader to project these vertices to (0,0,0), dependent on the input color. You could define your transparent black and not show any black triangles. Like so:
PS_IN VS( VS_IN input)
{
PS_IN output = (PS_IN)0;
if ((input.color[0]!=0)||(input.color[1]!=0)||(input.color[2]!=0))
{
output.position = mul(worldViewProj,input.position);
}
output.color = input.color;
return output;
}
See below the effect on the edges of my HeightField mesh, on the left is the unchanged version..
NOTE: The latter solution gives sharper edges, but it only works when (0,0,0) is behind the object.