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Fix GPU Particles 

The special case atan(y,0) of the built-in shader function atan(y,x)
returns different results on different devices. So this commit will add
checks when the atan(y,x) function is used in ParticlesMaterial to set
the direction of GPU Particles to make sure the desired values are
returned (act as atan2(y,x)).

(cherry picked from commit 3580ad6005)
This commit is contained in:
zxcvdev 2020-02-08 21:32:01 +01:00 committed by Rémi Verschelde
parent 93b99f2c89
commit 6380943831
1 changed files with 6 additions and 3 deletions
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9
scene/resources/particles_material.cpp
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@ -316,14 +316,17 @@ void ParticlesMaterial::_update_shader() {
if (flags[FLAG_DISABLE_Z]) {
code += " float angle1_rad = atan(direction.y, direction.x) + rand_from_seed_m1_p1(alt_seed) * spread_rad;\n";
code += " float angle1_rad = rand_from_seed_m1_p1(alt_seed) * spread_rad;\n";
code += " angle1_rad += direction.x != 0.0 ? atan(direction.y, direction.x) : sign(direction.y) * (pi / 2.0);\n";
code += " vec3 rot = vec3(cos(angle1_rad), sin(angle1_rad), 0.0);\n";
code += " VELOCITY = rot * initial_linear_velocity * mix(1.0, rand_from_seed(alt_seed), initial_linear_velocity_random);\n";
} else {
//initiate velocity spread in 3D
code += " float angle1_rad = atan(direction.x, direction.z) + rand_from_seed_m1_p1(alt_seed) * spread_rad;\n";
code += " float angle2_rad = atan(direction.y, abs(direction.z)) + rand_from_seed_m1_p1(alt_seed) * spread_rad * (1.0 - flatness);\n";
code += " float angle1_rad = rand_from_seed_m1_p1(alt_seed) * spread_rad;\n";
code += " float angle2_rad = rand_from_seed_m1_p1(alt_seed) * spread_rad * (1.0 - flatness);\n";
code += " angle1_rad += direction.z != 0.0 ? atan(direction.x, direction.z) : sign(direction.x) * (pi / 2.0);\n";
code += " angle2_rad += direction.z != 0.0 ? atan(direction.y, abs(direction.z)) : (direction.x != 0.0 ? atan(direction.y, abs(direction.x)) : sign(direction.y) * (pi / 2.0));\n";
code += " vec3 direction_xz = vec3(sin(angle1_rad), 0.0, cos(angle1_rad));\n";
code += " vec3 direction_yz = vec3(0.0, sin(angle2_rad), cos(angle2_rad));\n";
code += " direction_yz.z = direction_yz.z / max(0.0001,sqrt(abs(direction_yz.z))); // better uniform distribution\n";