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Asked: 2026-05-19T11:39:34+00:00

I am trying to make a shader that simulates the sun position and the

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I am trying to make a shader that simulates the sun position and the light that it reflects in a object.

To simulate the sun trajectory I have a timer, and the light position is defined by:

fvLightPosition.x=-cos(Time)*speed;
fvLightPosition.y=sin(Time)*speed;
fvLightPosition.z=100.0;

The timer is a variable float Time0_X

I almost get the right trajectory, except that is upside down, and somehow look a bit weird. Can anyone give me a tip how to simulate the sun trajectory in the right way?

I am using RenderMonkey to make the shader.

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1 Answer

  1. Editorial Team

    Make sure that you scale your Time value so that it lies between 0 and 2*PI radians (which corresponds to 0 and 180 degrees respectively). If your original Time value ranges from 0 to some number MAX, you can do the scaling like this: (Time / MAX) * 2PI.

    I’m not sure what speed refers to, but you should most likely not be multiplying by that. The cos and sin values represent the X and Y components of the vector between the sun and the origin, so you should multiply by the distance of the sun from the centre of your scene, which is usually constant.

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