4 replies to this topic

[Jeason]

void VertShadowVolume( float4 vPos : POSITION,
					   float3 vNormal : NORMAL,
					   out float4 oPos : POSITION )
{
    // Compute view space normal
    float3 N = mul( vNormal, (float3x3)g_mWorldView );

    // Obtain view space position
    float4 PosView = mul( vPos, g_mWorldView );

    // Light-to-vertex vector in view space
    float3 LightVecView = PosView - g_vLightView;

    // Perform reverse vertex extrusion
    // Extrude the vertex away from light if it's facing away from the light.
    if( dot( N, -LightVecView ) < 0.0f )
    {
	    if( PosView.z > g_vLightView.z )
		    PosView.xyz += LightVecView * ( g_fFarClip - PosView.z ) / LightVecView.z;
	    else
		    [color=#ff0000]PosView = float4( LightVecView, 0.0f );[/color]

	    // Transform the position from view space to homogeneous projection space
	    oPos = mul( PosView, g_mProj );
    } else
 
	    oPos = mul( vPos, g_mWorldViewProjection );
}

I can't understand the red line.

When the vertex is closer to viewer than light, we can also add PosView with some LightVecView.
But it just changes the position to a vector.
What is the meaning of the red line?

[Jeason]

The red line doesn't present.

It's PosView = float4( LightVecView, 0.0f );.

[Hodgman]

"If the light is between the camera and the vertex, then the vertex is moved off into the distance, else the vertex is moved behind the camera by "LightVecView" (PosView.z - g_vLightView.z) units.".

[Jeason]

Hodgman, on 22 February 2012 - 07:38 AM, said:

"If the light is between the camera and the vertex, then the vertex is moved off into the distance, else the vertex is moved behind the camera by "LightVecView" (PosView.z - g_vLightView.z) units.".

Thank you, Hodgman.

If you are right, then the vertex doesn't move along the line between light and vertex, but the line between light and camera when the vertex is closer to camera than light.
But we should move along the line between light and vertex.

[Jeason]

And why does it make float4( LightVecView, 0 ), not float4( LightVecView, 1 );