Приклади вживання The shadow map Англійська мовою та їх переклад на Українською
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For access to the shadow map.
Attach the shadow map to framebuffer.
Following image depicts example of the shadow map.
The shadow map from first rendering pass.
Texture coordinates for access to the shadow map.
Sampling from the shadow map returns distance to point Dref.
Offset by two units equal to smallest value of change in the shadow map.
Usage of the shadow map for shadowing tests.
Depth is stored in z-buffer to which the shadow map is attached.
For rendering into the shadow map, we also need to create a framebuffer.
Size of the viewport should be equal to size of the shadow map.
The shadow map is passed to the fragment shader of second rendering pass.
In the fragment shader, this position is used to sample from the shadow map.
The shadow map is attached to framebuffer to GL_DEPHT_ATTACHMENT slot.
Variance Shadow Mapping(VSM)method calculates soft shadows and requires only one sample from the shadow map.
Following code snippet shows how to create the shadow map and framebuffer for rendering to the shadow map:. .
Let's call this new matrix- shadowMat. Through transform of a vertex with shadowMat we are getting texturecoordinates that can be used to sample the shadow map.
Offset should depend on precision of the shadow map, and on slope of the surface relative to direction to light source.
First image depicts results of shadow mapping with size of the shadow map equal to 1024 texels.
After first rendering pass, the shadow map contains distances to closest objects from light source's point of view in each texel.
Second image depicts results of shadow mapping with size of the shadow map equal to 256 texels.
So each texel of the shadow map contains distance to the closest point to the light source, which is lightened, and doesn't lie in the shadow. .
Distance(depth) from the light source to objects closest to the light source is saved to the texture- the shadow map.
For correct work of shadow mapping method, space that is saved into the shadow map should contain space that is visible through the camera.
If the distance from the shadow map is lower than the distance from the current fragment to the light source, then current fragment is in the shadow as it lies behind another surface, distance to which was saved to the shadow map in the first rendering pass.
Following image depicts objects in the scene(green figures), source of light andvolume of space for which distances will be saved to the shadow map. Surfaces for which distance will be saved to the shadow map is marked with light blue.
Aliasing and artifacts are because the shadow map is the discrete texture and saves only finite number of distance from the source of light to objects in the scene.
With the help of screen space position(relative to the light source) of the fragment,it's possible to sample the shadow map and to get the distance to the closest object on the direction from the light source to the current fragment.
Surface behind the circle andthe opposite side of the circle don't affect the shadow map as they are invisible from light source's point of view(closer part of the circle occludes surfaces behind it).