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https://github.com/kevinbentley/Descent3.git
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58 lines
2.3 KiB
GLSL
58 lines
2.3 KiB
GLSL
#version 150 core
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/*
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* Descent 3
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* Copyright (C) 2024 Descent Developers
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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in vec4 vertex_color;
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in vec2 vertex_uv0;
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in vec2 vertex_uv1;
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in vec4 vertex_modelview_pos;
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out vec4 out_color;
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uniform sampler2D u_texture0;
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uniform sampler2D u_texture1;
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uniform int u_texture_enable;
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uniform bool u_fog_enable;
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uniform vec4 u_fog_color;
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uniform float u_fog_start;
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uniform float u_fog_end;
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float branchless_invert_or_zero(in float value) {
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// sign() returns 1 if val > 0, -1 if val < 0, and 0 if val == 0
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float sign_squared = sign(value) * sign(value);
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// so this will either be 1/value, or 0/-1
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return sign_squared / (value + sign_squared - 1.0);
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}
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void main()
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{
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out_color = vertex_color
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// take advantage of the fact that we're multiplying to make vec4(1) represent a "disabled"
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// texture sample. a real sample will always have component values <= 1, bool is defined
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// to cast to either 0 or 1, so taking the max() of the sample and an _inverted_ enable
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// signal lets this ignore a texture w/o branching. we use a bitfield to save bandwidth.
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* max(texture(u_texture0, vertex_uv0), vec4(float(!bool((u_texture_enable >> 0) & 1))))
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* max(texture(u_texture1, vertex_uv1), vec4(float(!bool((u_texture_enable >> 1) & 1))));
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float fog_factor = clamp((u_fog_end - length(vertex_modelview_pos)) * branchless_invert_or_zero(u_fog_end - u_fog_start), 0, 1);
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// out_color is unchanged when fog_factor is 1 (ie, fog distance == u_fog_start). thus, to disable,
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// fog_factor must also be 1. invert u_fog_enable (so that it is 1 when disabled) and take the max.
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fog_factor = max(fog_factor, float(!u_fog_enable));
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out_color = out_color * fog_factor + (1 - fog_factor) * u_fog_color;
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} |