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backend: gl_common: Use texture2D with filtering and clamping in blur

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Create texture with GL_LINEAR filtering and GL_CLAMP_TO_EDGE wrapping. Change
`texelFetch()`-call in fragement shader to `texture2D()` to be taken into
account. This requires supplying the size of a pixel in normalized texture
coordinates via an additional uniform.

Fixes darkening at the screen edges with larger blur radii caused by
sampling coordinates being out of texture bounds. This is undefined behaviour
unless the context has set the flag *GL_ARB_robust_buffer_access_behaviour*,
in which case "zero"-pixels are returned (i.e. black). Current behaviour
seems to depend on the driver.
This commit is contained in:
Bernd Busse 2020-06-06 21:27:25 +02:00
parent fd6ff8264c
commit 4b0ff37b36
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GPG key ID: 6DD2A3C48E63A5AB
2 changed files with 29 additions and 10 deletions
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35
src/backend/gl/gl_common.c
View file

@ -629,20 +629,27 @@ bool gl_blur(backend_t *base, double opacity, void *ctx, const region_t *reg_blu
// The origin to use when sampling from the source texture
GLint texorig_x, texorig_y;
GLint tex_width, tex_height;
GLuint src_texture;
if (i == 0) {
texorig_x = extent_resized->x1;
texorig_y = dst_y_resized_screen_coord;
tex_width = gd->width;
tex_height = gd->height;
src_texture = gd->back_texture;
} else {
texorig_x = 0;
texorig_y = 0;
tex_width = bctx->texture_width;
tex_height = bctx->texture_height;
src_texture = bctx->blur_texture[curr];
}
glBindTexture(GL_TEXTURE_2D, src_texture);
glUseProgram(p->prog);
glUniform2f(p->unifm_pixel_norm, 1.0f / (GLfloat)tex_width,
1.0f / (GLfloat)tex_height);
if (i < bctx->npasses - 1) {
// not last pass, draw into framebuffer, with resized regions
glBindVertexArray(vao[1]);
@ -976,19 +983,20 @@ void *gl_create_blur_context(backend_t *base, enum blur_method method, void *arg
// clang-format off
static const char *FRAG_SHADER_BLUR = GLSL(330,
%s\n // other extension pragmas
uniform sampler2D tex_scr;
uniform sampler2D tex_src;
uniform vec2 pixel_norm;
uniform float opacity;
in vec2 texcoord;
out vec4 out_color;
void main() {
vec2 uv = texcoord * pixel_norm;
vec4 sum = vec4(0.0, 0.0, 0.0, 0.0);
%s //body of the convolution
out_color = sum / float(%.7g) * opacity;
}
);
static const char *FRAG_SHADER_BLUR_ADD = QUOTE(
sum += float(%.7g) *
texelFetch(tex_scr, ivec2(texcoord + vec2(%d, %d)), 0);
sum += float(%.7g) * texture2D(tex_src, uv + pixel_norm * vec2(%d, %d));
);
// clang-format on
@ -1042,6 +1050,8 @@ void *gl_create_blur_context(backend_t *base, enum blur_method method, void *arg
glBindFragDataLocation(pass->prog, 0, "out_color");
// Get uniform addresses
pass->unifm_pixel_norm =
glGetUniformLocationChecked(pass->prog, "pixel_norm");
pass->unifm_opacity = glGetUniformLocationChecked(pass->prog, "opacity");
pass->orig_loc = glGetUniformLocationChecked(pass->prog, "orig");
pass->texorig_loc = glGetUniformLocationChecked(pass->prog, "texorig");
@ -1061,6 +1071,7 @@ void *gl_create_blur_context(backend_t *base, enum blur_method method, void *arg
// the single pass case
auto pass = &ctx->blur_shader[1];
pass->prog = gl_create_program_from_str(vertex_shader, dummy_frag);
pass->unifm_pixel_norm = -1;
pass->unifm_opacity = -1;
pass->orig_loc = glGetUniformLocationChecked(pass->prog, "orig");
pass->texorig_loc = glGetUniformLocationChecked(pass->prog, "texorig");
@ -1079,11 +1090,15 @@ void *gl_create_blur_context(backend_t *base, enum blur_method method, void *arg
// Texture size will be defined by gl_blur
glGenTextures(2, ctx->blur_texture);
glBindTexture(GL_TEXTURE_2D, ctx->blur_texture[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glBindTexture(GL_TEXTURE_2D, ctx->blur_texture[1]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
// Generate FBO and textures when needed
glGenFramebuffers(1, &ctx->blur_fbo);
if (!ctx->blur_fbo) {
@ -1196,8 +1211,10 @@ bool gl_init(struct gl_data *gd, session_t *ps) {
}
glBindTexture(GL_TEXTURE_2D, gd->back_texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glBindTexture(GL_TEXTURE_2D, 0);
// Set projection matrix to gl viewport dimensions so we can use screen

4
src/backend/gl/gl_common.h
View file

@ -32,6 +32,7 @@ typedef struct {
// Program and uniforms for blur shader
typedef struct {
GLuint prog;
GLint unifm_pixel_norm;
GLint unifm_opacity;
GLint orig_loc;
GLint texorig_loc;
@ -168,7 +169,8 @@ static inline void gl_check_err_(const char *func, int line) {
}
static inline void gl_clear_err(void) {
while (glGetError() != GL_NO_ERROR);
while (glGetError() != GL_NO_ERROR)
;
}
#define gl_check_err() gl_check_err_(__func__, __LINE__)