Jump to content
  • Advertisement
Sign in to follow this  

Shimmering Shadow Edges

This topic is 2182 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I've been messing around with a basic shadow map implementation, and trying out approaches to dealing with the various artifacts.  While reading this Direct3D article on MSDN: Common Techniques to Improve Shadow Depth Maps, there is a section 'Moving the Light in Texel-Sized Increments' which seemed to have a simple solution that I could use, but I must be missing something in my implementation because I can't get rid of the shimmering...


The concept of quantizing the movement of the light frustum makes sense:

vLightCameraOrthographicMin /= vWorldUnitsPerTexel;
vLightCameraOrthographicMin = XMVectorFloor(vLightCameraOrthographicMin);
vLightCameraOrthographicMin *= vWorldUnitsPerTexel;
vLightCameraOrthographicMax /= vWorldUnitsPerTexel;
vLightCameraOrthographicMax = XMVectorFloor(vLightCameraOrthographicMax);
vLightCameraOrthographicMax *= vWorldUnitsPerTexel;

but the article glosses over a few details that leave me puzzled.  In particular the statement "The vWorldUnitsPerTexel value is calculated by taking a bound of the view frustum, and dividing by the buffer size." and the following bit of code:

FLOAT fWorldUnitsPerTexel = fCascadeBound / (float)m_CopyOfCascadeConfig.m_iBufferSize;        
vWorldUnitsPerTexel = XMVectorSet(fWorldUnitsPerTexel, fWorldUnitsPerTexel, 0.0f, 0.0f);

I don't understand how to get the fCascadeBound value, and I assume the divisor in the expression is the shadow map resolution?  Also, the vLightCameraOrthographicMin and Max values are in light view space, is that correct?





Share this post

Link to post
Share on other sites

After a lot of trial and error I was able to get it to work.  Since my light frustum dimensions are fixed, I convert the center point into texel space, floor the X and Y coordinates, then convert it back to world space:

// (sceneBounds.Center has been placed based on the camera frustum.)
sceneBounds.Radius = 50.0f;

float texelsPerWorldUnit = (float)SMAP_SIZE / (sceneBounds.Radius * 2.0f);

Matrix lightViewAtOrigin = Matrix.CreateScale(texelsPerWorldUnit) *
    Matrix.CreateLookAt(Vector3.Zero, -sceneLights[0].Direction, Vector3.Up);

Matrix lightViewAtOriginInv = Matrix.Invert(lightViewAtOrigin);

sceneBounds.Center = Vector3.Transform(sceneBounds.Center, lightViewAtOrigin);
sceneBounds.Center.X = (float)(Math.Floor(sceneBounds.Center.X));
sceneBounds.Center.Y = (float)(Math.Floor(sceneBounds.Center.Y));
sceneBounds.Center = Vector3.Transform(sceneBounds.Center, lightViewAtOriginInv);

lightView = Matrix.CreateLookAt(sceneBounds.Center - sceneLights[0].Direction * 
    sceneBounds.Radius * 2.0f, sceneBounds.Center, Vector3.Up);
lightFrustum = Matrix.CreateOrthographic(sceneBounds.Radius * 2.0f,
    sceneBounds.Radius * 2.0f, 0.0f, sceneBounds.Radius * 6.0f);


Edited by Tengato

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!