36 lines
953 B
Plaintext
36 lines
953 B
Plaintext
#version 150 compatibility
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in SphereData {
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vec2 q_tilde;
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float inv_e;
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vec3 nml_e_eye;
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vec3 nml_v_eye;
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vec2 zw_e_clip;
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vec2 zw_v_clip;
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vec3 v_eye;
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} Fin;
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bool compute_sphere_intersection(out float depth, out vec3 p_eye, out vec3 n_eye, in bool show_backside = false)
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{
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// check for intersection
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float q_tilde_squared_length = dot(Fin.q_tilde, Fin.q_tilde);
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if (q_tilde_squared_length > 1.0)
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return false;
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// compute ray parameter
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float beta = Fin.inv_e*sqrt(1.0 - q_tilde_squared_length);
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float lambda = show_backside ? 1.0 / (1.0 - beta) : 1.0 / (1.0 + beta);
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// depth correction
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vec2 zw = Fin.zw_e_clip + lambda * Fin.zw_v_clip;
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float z_clip = zw.x / zw.y;
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depth = 0.5*(z_clip + 1.0); // transform from [-1,1] to [0,1]
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// compute sphere position and normal in eye coordinates
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p_eye = lambda*Fin.v_eye;
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n_eye = normalize(Fin.nml_e_eye + lambda * Fin.nml_v_eye);
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if (show_backside) {
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n_eye = -n_eye;
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}
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return true;
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} |