[EAE 6900-026] Write-Up 14

Cubemap

Posted by Zhitao on April 24, 2019

Cubemap

The game

Click to download the Game

Controls

Use mouse to control direction.

Press W, A, S, D to move the main camera.

Cubemap

Before we use 2D textures and use uv position to sample. A cubemap is basically a texture that contains 6 individual 2D textures that each form one side of a cube: a textured cube. The advantage of cubemap is that we can use a 3D vector such as direction vector to sample and we can use any tricks we know in shaders to get this vector.

Building a cube texture is basically the same as other kinds of textures. In my game, I only used a single cube texture for making a skybox and doing environment mapping.

Skybox

Skybox is a big cube that will move with the camera. In fragment shader, I used the local position (which is equal to direction vector) of each fragment to sample the cubemap.

o_color = SampleTextureCube(g_cubemap_texture, g_samplerState, i_samplePosition);

Environment Map

By using cubemap, we can make many interesting effects. These effects are called environment mapping. The most popular one should be reflection.

We use view vector and normal vector to calculate the reflection vector, and use the result to sample on the cubemap. Then we can get a environment lighting.

In my gold metal material, there’s no diffuse light. Both specular and environment reflection are multiplied by a yellow color. And in my earth material, since the glossness of sea part is 256, it looks very smooth. The land part doesn’t have any reflection.