Quote:Original post by bushmanpaul
1.The small bands of light you are seeing is the inaccuracy in float. This is totally normal.

2.This is also a problem with inaccuracy with float, try adding more bias (might make small bands of light bigger).

http://developer.nvidia.com/object/hwshadowmap_paper.html shows you how to solve this.

3.The further the light is away the higher your shadow Map resolution need to be for you to get better results.If I understand you correctly.

Hope this helps.

Quote:Original post by rouncED
you can use a 32 bit floating point texture, use view space z and then thatll work better maybe?

Quote:Original post by MJP

Quote:Original post by xytor

Quote:Original post by rouncED
you can use a 32 bit floating point texture, use view space z and then thatll work better maybe?

I already use a 32 bit texture: D3DFMT_X8R8G8B8
Also, I already use the view space z. That's why it can be any value between clipNear and clipFar, right?

He said 32-bit floating point texture, for example D3DFMT_R32F. 8-bits is not going to have sufficient precision for a shadow map. Plus an integer format is going to be clamped to [0,1], so you can't store view-space z in it.

Quote:Original post by MJP
No you still return a float4 from your pixel shader. You can just return 1.0f for the BGA components. When you sample the texture you will still get a float4, but only the first component will be valid. The other 3 will either be 0 or 1, depending on the GPU and driver.

Quote:Original post by MJP
In general for a spotlight the projection for the shadow map should be wide enough that the entire cone-shaped area of the light fits within the borders of the shadow map. So if you're sampling past the border then your projection isn't wide enough. You should make the FOV based on the angular attenuation factor you're using for the spotlight, rather than hard-coding it. Aside from that, also make sure that you have POINT sampling enabled when sampling the shadow map.

The reason it fails when the light is vertical is because you hard-coded the up vector of your view matrix as (0,1,0). So when the light's look direction is parallel to that vector (looking straight up or straight down) the view matrix becomes invalid, since the cross product of parallel vectors is zero. A simple fix is to just test for that case and use a different up vector. Or you can use something like this to always generate an up vector that's perpendicular to your lookAt direction.

Shadows for directional lights are a broad topic, and it's not trivial to implement them properly and avoid aliasing problems. Since a directional light is global you can't just make a view and projection based on a light position and direction like you can with a spot light. Instead you have to fit an orthographic projection to the main camera's view frustum. On top of that you also need to a technique to reduce perspective aliasing caused by the non-rectangular shape of the view frustum. Cascaded shadow maps (CSM) are the most popular for this. If you do some searches on the forum or on Google you should be able to find more information about directional shadow maps in general, and CSM.