88 lines
2.7 KiB
GLSL
88 lines
2.7 KiB
GLSL
// SuperTuxKart - a fun racing game with go-kart
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// Copyright (C) 2013 the SuperTuxKart team
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 3
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// of the License, or (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, write to the Free Software
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// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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// motion_blur.frag
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// The actual boost amount (which linearly scales the blur to be shown).
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// should be in the range [0.0, 1.0], though a larger value might make
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// the blurring too string. Atm we are using [0, 0.5].
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#version 130
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uniform float boost_amount;
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// The color buffer to use.
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uniform sampler2D color_buffer;
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// Center (in texture coordinates) at which the kart is. A small circle
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// around this center is not blurred (see mask_radius below)
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uniform vec2 center;
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// The direction to which the blurring aims at
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uniform vec2 direction;
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// Radius of mask around the character in which no blurring happens
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// so that the kart doesn't get blurred.
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uniform float mask_radius;
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// Maximum height of texture used
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uniform float max_tex_height;
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out vec4 FragColor;
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// Number of samples used for blurring
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#define NB_SAMPLES 8
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void main()
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{
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vec2 texcoords = gl_TexCoord[0].st;
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// Sample the color buffer
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vec3 color = texture(color_buffer, texcoords).rgb;
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// Compute the blur direction.
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// IMPORTANT: we don't normalize it so that it avoids a glitch around 'center',
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// plus it naturally scales the motion blur in a cool way :)
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vec2 blur_dir = direction - texcoords;
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// Compute the blurring factor:
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// - apply the mask, i.e. no blurring in a small circle around the kart
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float blur_factor = max(0.0, length(texcoords - center) - mask_radius);
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// - avoid blurring the top of the screen
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blur_factor *= (max_tex_height - texcoords.t);
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// - apply the boost amount
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blur_factor *= boost_amount;
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// Scale the blur direction
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blur_dir *= blur_factor;
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// Compute the blur
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vec2 inc_vec = blur_dir / vec2(NB_SAMPLES);
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vec2 blur_texcoords = texcoords + inc_vec;
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for(int i=1 ; i < NB_SAMPLES ; i++)
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{
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color += texture(color_buffer, blur_texcoords).rgb;
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blur_texcoords += inc_vec;
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}
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color /= vec3(NB_SAMPLES);
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FragColor = vec4(color, 1.0);
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// Keep this commented line for debugging:
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//FragColor = vec4(blur_factor, blur_factor, blur_factor, 0.0);
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}
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