1.1 KiB
Task 2
a)
What is the name of this phenomenon?
Clipping
When does it occur?
It occurs when some part of an object is outside the clipping volume which is a 2x2x2 cube at the origin with coordinate values ranging from -1 to 1. Since the z coordinate for v0 and v1 is 1.2 and -1.2, whic is outside this range, the triangle is clipped by the vertex shader and the part which sticks out is not rendered. The two corners have essentially been clipped off by the clip box.
What is its purpose?
The clip box ensures that objects behind the camera and generally when geometry exceeds the bounds of the screen.
b)
What happens?
The triangle is no longer visible.
Why does it happen?
This is because of back-face culling. When the triangle is deemed to be facing away from the camera it is culled. And thus not rendered.
What is the condition under which this effect occurs?
If the cross product of two arbitrary edges of a triangle, which respects the vertex order is negative. Because of this the ordering in the index buffer is important since it determines which wheter or not the triangle is considered facing away or towards the camera.