ebiten/internal/graphics/shader.go

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// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
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package graphics
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import (
"strings"
)
type shaderID int
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const (
shaderVertexModelview shaderID = iota
shaderFragmentNearest
shaderFragmentLinear
shaderFragmentScreen
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)
func shader(id shaderID) string {
if id == shaderVertexModelview {
return shaderStrVertex
}
defs := []string{}
switch id {
case shaderFragmentNearest:
defs = append(defs, "#define FILTER_NEAREST")
case shaderFragmentLinear:
defs = append(defs, "#define FILTER_LINEAR")
case shaderFragmentScreen:
defs = append(defs, "#define FILTER_SCREEN")
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default:
panic("not reached")
}
return strings.Replace(shaderStrFragment, "{{Definitions}}", strings.Join(defs, "\n"), -1)
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}
const (
shaderStrVertex = `
uniform mat4 projection_matrix;
attribute vec2 vertex;
attribute vec4 tex_coord;
attribute vec4 color_scale;
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varying vec2 varying_tex_coord;
varying vec2 varying_tex_coord_min;
varying vec2 varying_tex_coord_max;
varying vec4 varying_color_scale;
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void main(void) {
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varying_tex_coord = vec2(tex_coord[0], tex_coord[1]);
if (tex_coord[2] >= 0.0 && tex_coord[3] >= 0.0) {
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varying_tex_coord_min = vec2(min(tex_coord[0], tex_coord[2]), min(tex_coord[1], tex_coord[3]));
varying_tex_coord_max = vec2(max(tex_coord[0], tex_coord[2]), max(tex_coord[1], tex_coord[3]));
} else {
varying_tex_coord_min = vec2(0, 0);
varying_tex_coord_max = vec2(1, 1);
}
varying_color_scale = color_scale;
gl_Position = projection_matrix * vec4(vertex, 0, 1);
}
`
shaderStrFragment = `
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#if defined(GL_ES)
precision mediump float;
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#else
#define lowp
#define mediump
#define highp
#endif
{{Definitions}}
uniform sampler2D texture;
uniform mat4 color_matrix_body;
uniform vec4 color_matrix_translation;
uniform highp vec2 source_size;
#if defined(FILTER_SCREEN)
uniform highp float scale;
#endif
varying highp vec2 varying_tex_coord;
varying highp vec2 varying_tex_coord_min;
varying highp vec2 varying_tex_coord_max;
varying highp vec4 varying_color_scale;
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// adjustTexel adjusts the two texels and returns the adjusted second texel.
// When p1 - p0 is exactly equal to the texel size, jaggy can happen on macOS (#669).
// In order to avoid this jaggy, subtract a little bit from the second texel.
highp vec2 adjustTexel(highp vec2 p0, highp vec2 p1) {
highp vec2 texel_size = 1.0 / source_size;
if (fract((p1.x-p0.x)*source_size.x) == 0.0) {
p1.x -= texel_size.x / 512.0;
}
if (fract((p1.y-p0.y)*source_size.y) == 0.0) {
p1.y -= texel_size.y / 512.0;
}
return p1;
}
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void main(void) {
highp vec2 pos = varying_tex_coord;
highp vec2 texel_size = 1.0 / source_size;
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#if defined(FILTER_NEAREST)
vec4 color = texture2D(texture, pos);
if (pos.x < varying_tex_coord_min.x ||
pos.y < varying_tex_coord_min.y ||
(varying_tex_coord_max.x - texel_size.x / 512.0) <= pos.x ||
(varying_tex_coord_max.y - texel_size.y / 512.0) <= pos.y) {
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color = vec4(0, 0, 0, 0);
}
#endif
#if defined(FILTER_LINEAR)
highp vec2 p0 = pos - texel_size / 2.0;
highp vec2 p1 = pos + texel_size / 2.0;
p1 = adjustTexel(p0, p1);
vec4 c0 = texture2D(texture, p0);
vec4 c1 = texture2D(texture, vec2(p1.x, p0.y));
vec4 c2 = texture2D(texture, vec2(p0.x, p1.y));
vec4 c3 = texture2D(texture, p1);
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if (p0.x < varying_tex_coord_min.x) {
c0 = vec4(0, 0, 0, 0);
c2 = vec4(0, 0, 0, 0);
}
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if (p0.y < varying_tex_coord_min.y) {
c0 = vec4(0, 0, 0, 0);
c1 = vec4(0, 0, 0, 0);
}
if ((varying_tex_coord_max.x - texel_size.x / 512.0) <= p1.x) {
c1 = vec4(0, 0, 0, 0);
c3 = vec4(0, 0, 0, 0);
}
if ((varying_tex_coord_max.y - texel_size.y / 512.0) <= p1.y) {
c2 = vec4(0, 0, 0, 0);
c3 = vec4(0, 0, 0, 0);
}
vec2 rate = fract(p0 * source_size);
vec4 color = mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y);
#endif
#if defined(FILTER_SCREEN)
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highp vec2 p0 = pos - texel_size / 2.0 / scale;
highp vec2 p1 = pos + texel_size / 2.0 / scale;
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p1 = adjustTexel(p0, p1);
vec4 c0 = texture2D(texture, p0);
vec4 c1 = texture2D(texture, vec2(p1.x, p0.y));
vec4 c2 = texture2D(texture, vec2(p0.x, p1.y));
vec4 c3 = texture2D(texture, p1);
// Texels must be in the source rect, so it is not necessary to check that like linear filter.
vec2 rateCenter = vec2(1.0, 1.0) - texel_size / 2.0 / scale;
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vec2 rate = clamp(((fract(p0 * source_size) - rateCenter) * scale) + rateCenter, 0.0, 1.0);
vec4 color = mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y);
#endif
// Un-premultiply alpha
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if (0.0 < color.a) {
color.rgb /= color.a;
}
// Apply the color matrix or scale.
color = (color_matrix_body * color) + color_matrix_translation;
color *= varying_color_scale;
color = clamp(color, 0.0, 1.0);
// Premultiply alpha
color.rgb *= color.a;
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gl_FragColor = color;
}
`
)