Graphics Programming 12

Finally! Shadows!

To be honest, after doing the depth technique for soft intersection effect, this one is not that hard. All we need to do is to add another pass for the shadow map. The process is almost the same as the depth pass, the only difference is instead of using the world to view, view to projected transform, we use world to light, light to projected transform, since the "depth" in light's view is how we determine which part of the object should be lit or not.

Again, most of the time is spent on debugging, thanks to PIX, I managed to locate most of the bugs pretty fast.

Here is one of the core part of shadowing:

float shadowModifier;
{
float3 position_projected = i_lightProjectedPosition.xyz/ i_lightProjectedPosition.w;
float2 texcoord_screen = (i_lightProjectedPosition.xy * float2(0.5, -0.5)) + 0.5;
float current_depth = i_shadowDepth;
float depth_previous = tex2D(g_shadowMapSampler, texcoord_screen).x;
depth_previous *= g_farClipPlaneDistanceForShadow;
shadowModifier = current_depth < depth_previous + 1.0f;
}

float3 diffuseLighting = lightColor * lightIntensity * strength + g_directionalLightColor.xyz * directionalLightStrength* shadowModifier;
float4 lighting = float4(diffuseLighting, 1.0) + g_ambientLightColor;

Since I have two lights in the scene, I only made shadows influence the directional light, which makes the shadow less "black" and more real.

Here is a screen shot of the scene:

To Control the directional light:
U - back, O - forward, J - left, L - right, I - up, K - down.

WASD - controls all the objects.

The shadow map in PIX:

Link of the code:
Graphics 12