Shadow contact issue in sample shadow-sapp.c

Hi

There is a shadow contact issue in the sample shadow-sapp.c.
You see it when the cube is near the floor.
Compiled with gcc & VSCode

To show the issue just added a float variable cy to the state struct and the following lines at 218:

    state.cy += 0.01 * t;
    float fff = sin(state.cy) * 2 + 0.95;
    const hmm_mat4 translate = HMM_Translate(HMM_Vec3(0,fff,0));

In fact it can be 'fixed' by adding 0.001 to the depth at line 154 of shadow-sapp.glsl

float depth = lightPos.z+0.001;

But that is purely by trying instead of understanding what I am doing ahaha

I found this as well & had the same feeling of 'lol idk what im doing'.
Then I studied it for like a week.

I fixed it by using CULLMODE_FRONT on the shadow pass and adding a bias in the shader to get rid of self-shadowing

        float bias = max(0.008 * (1.0 - n_dot_l), 0.0005);
        sm_pos.z = sm_pos.z - bias;

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