So, one of the exercises for my computer graphics class is as follows:

Calculate the shadow cast by triangle T onto the YZ plane P.


  • Triangle T coordinates: A=(30,10,16) B=(32,11,18) C=(31,12,24)
  • Light source L=(40,10,18)

The scene described above is as follows: there is a light source emitting light onto a triangle, the triangle is in front of a plane, due to the light there will be a shadow cast formed onto the plane.

In other exercises where we had to calculate whether or not a point was inside the shadow cast we made use of a line/plane equation. But this time it is not clear for me how calculate the points of the shadow cast.


Find the equation of each line that starts on the light and goes through a vertex of the triangle. Then make the equation equal to the equation of the plane.

Basically, lightPosition + verticePosition = lineEquation.

Then lineEquation = lineOnThePlaneEquation

Here's an example


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