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feat(OpenGL renderer): add post presentation gamma control

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Some titles and enhancement mods/plugins might require display level gamma correction to improve shadow detail and overall visibility without altering guest rendering state. This introduces a public gamma adjustment interface for the OpenGL renderer via `gl_renderer_set_post_gamma`, that enables external plugins to adjust the display curve cleanly at runtime.

This adjustment applies exclusively to game content and temporal interpolation passes while leaving host interface elements, bezels, and previously composed frames untouched. Modifying the gamma setting immediately invalidates the presentation buffer so that changes become visible on screen without requiring new video memory writes from the guest system.
This commit is contained in:
Aliet Exposito Garcia
2026-09-13 01:30:10 -04:00
parent 3a275d4939
commit 72b3ead892
2 changed files with 68 additions and 8 deletions
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runtime/include/gpu_gl_renderer.h
+9
View File
@@ -130,6 +130,15 @@ void gl_renderer_set_display_aspect(int num, int den);
void gl_renderer_set_scanlines(int on, float strength);
int gl_renderer_get_scanlines(float *strength);
/* Presentation-only gamma adjustment. gamma = 1.0 is the identity; values
* above 1.0 lift shadow detail and values below 1.0 darken it. The adjustment
* is applied once to game content in the final GL presentation pass, including
* temporal interpolation, but not to the bezel, host OSD, black margins, or an
* already-composed hold-last image. Non-finite and out-of-range values are
* clamped to a safe range. Safe to call before GL context creation. */
void gl_renderer_set_post_gamma(float gamma);
float gl_renderer_get_post_gamma(void);
/* Select full native-wide mirror rendering instead of the centre-splice fast
* path. Textured edge expansion needs the complete mirror surface. */
void gl_renderer_set_wide_fast(int on);
runtime/src/gpu_gl_renderer.c
+59 -8
View File
@@ -320,6 +320,11 @@ static void gl_swap_with_osd(void);
static GLint s_present_uTex = -1, s_present_uUvRect = -1;
static GLint s_present_uTexSize = -1, s_present_uSharpScale = -1;
static GLint s_present_uSharp = -1;
static GLint s_present_uGamma = -1;
/* Host-side presentation state. The shader applies this only to the source
* image being presented; overlays and already-composed hold-last images set
* the uniform back to the identity explicitly. */
static float s_present_gamma = 1.0f;
/* Scanline post-process state (host display setting; see gl_renderer_set_scanlines).
* s_scanline_on/strength are pushed to whichever program draws game content;
* OSD/bezel and the already-composed hold-last re-present force it off so the
@@ -331,7 +336,7 @@ static GLint s_present_uScanLines = -1, s_present_uScanScale = -1;
static GLuint s_interp_prog = 0, s_interp_tex[3];
static GLint s_interp_uPrev = -1, s_interp_uCurr = -1;
static GLint s_interp_uAlpha = -1, s_interp_uUvRect = -1;
static GLint s_interp_uBlendMode = -1;
static GLint s_interp_uBlendMode = -1, s_interp_uGamma = -1;
static GLint s_interp_uScanline = -1, s_interp_uScanStrength = -1;
static GLint s_interp_uScanLines = -1, s_interp_uScanScale = -1;
static int s_interp_enabled = 0, s_interp_valid = 0;
@@ -776,7 +781,8 @@ static void letterbox_rect_aspect(int ww, int wh, int num, int den,
static void letterbox_rect(int ww, int wh, int *x, int *y, int *w, int *h);
static void present_target_quad(GLuint tex, int tex_w, int tex_h,
int x, int y, int w, int h, int linear,
int lx, int ly, int lw, int lh, int v_flip);
int lx, int ly, int lw, int lh, int v_flip,
int apply_gamma);
static void coh_record(int kind, int x0, int y0, int x1, int y1) {
GlCohEvent *e = &s_coh_ring[s_coh_seq % GL_COH_RING_CAP];
@@ -917,6 +923,7 @@ static const char *PRESENT_FS =
"uniform vec2 u_tex_size;\n"
"uniform vec2 u_sharp_scale;\n"
"uniform int u_sharp;\n"
"uniform float u_gamma;\n"
PSX_SCANLINE_UNIFORMS
/* Catmull-Rom bicubic via 9 bilinear taps. Sharper than plain bilinear at
* the same smoothness, with mild overshoot that reads as edge definition.
@@ -967,12 +974,13 @@ static const char *PRESENT_FS =
" c = texture(u_tex, uv);\n"
" }\n"
" c.rgb = psx_scanline(c.rgb, v_uv.y);\n"
" if (u_gamma > 0.0 && u_gamma != 1.0) c.rgb = pow(max(c.rgb, vec3(0.0)), vec3(1.0 / u_gamma));\n"
" frag = c;\n"
"}\n";
static const char *INTERP_FS =
"#version 330\n"
"in vec2 v_uv; uniform sampler2D u_prev; uniform sampler2D u_curr;\n"
"uniform float u_alpha; uniform int u_blend_mode; out vec4 frag;\n"
"uniform float u_alpha; uniform int u_blend_mode; uniform float u_gamma; out vec4 frag;\n"
PSX_SCANLINE_UNIFORMS
PSX_SCANLINE_FUNC
"void main(){\n"
@@ -986,6 +994,7 @@ static const char *INTERP_FS =
" }\n"
" vec4 c=mix(prev,curr,alpha);\n"
" c.rgb=psx_scanline(c.rgb, v_uv.y);\n"
" if (u_gamma > 0.0 && u_gamma != 1.0) c.rgb=pow(max(c.rgb, vec3(0.0)), vec3(1.0/u_gamma));\n"
" frag=c;\n"
"}\n";
@@ -2664,6 +2673,15 @@ static void present_set_sharp(int mode, int tex_w, int tex_h,
(float)out_h / (float)tex_h);
}
/* The presentation shader is shared by game content, bezel art, host OSD, and
* hold-last redraws. Uniform state persists across draws, so every draw must
* explicitly choose whether it is raw game content or an already-composed
* image. */
static void present_set_gamma(GLint uniform, int apply) {
if (uniform >= 0)
p_glUniform1f(uniform, apply ? s_present_gamma : 1.0f);
}
/* Push scanline uniforms into the currently-bound present or interpolation
* program.
* pitch_lines = the height of the TEXTURE that v_uv is normalized against
@@ -2724,6 +2742,29 @@ int gl_renderer_get_scanlines(float *strength) {
return s_scanline_on;
}
void gl_renderer_set_post_gamma(float gamma) {
if (!isfinite(gamma))
gamma = 1.0f;
if (gamma < 0.5f) gamma = 0.5f;
if (gamma > 3.0f) gamma = 3.0f;
if (fabsf(gamma - 1.0f) < 0.005f) gamma = 1.0f;
if (gamma == s_present_gamma)
return;
s_present_gamma = gamma;
/* Gamma is presentation state, not guest VRAM state. Invalidate the
* presentation latches so a hot change is visible on an unchanged frame.
* Force at least 2 frames so all backbuffers in the swapchain update. */
for (int i = 0; i < PRES_ROWS; i++) s_present_dirty[i] = ~0ull;
s_last_present_path = -1;
s_force_present_remaining = 2;
hold_invalidate();
}
float gl_renderer_get_post_gamma(void) {
return s_present_gamma;
}
/* Letterbox: largest num:den rect centered in the drawable. */
static void letterbox_rect_aspect(int ww, int wh, int num, int den,
int *x, int *y, int *w, int *h) {
@@ -2985,6 +3026,8 @@ int gl_renderer_init_context(SDL_Window *win) {
p_glGetUniformLocation(s_present_prog, "u_sharp_scale");
s_present_uSharp =
p_glGetUniformLocation(s_present_prog, "u_sharp");
s_present_uGamma =
p_glGetUniformLocation(s_present_prog, "u_gamma");
s_present_uScanline =
p_glGetUniformLocation(s_present_prog, "u_scanline");
s_present_uScanStrength =
@@ -3007,6 +3050,8 @@ int gl_renderer_init_context(SDL_Window *win) {
s_interp_uUvRect = p_glGetUniformLocation(s_interp_prog, "u_uv_rect");
s_interp_uBlendMode =
p_glGetUniformLocation(s_interp_prog, "u_blend_mode");
s_interp_uGamma =
p_glGetUniformLocation(s_interp_prog, "u_gamma");
glGenTextures(3, s_interp_tex);
for (int i = 0; i < 3; i++) {
glBindTexture(GL_TEXTURE_2D, s_interp_tex[i]);
@@ -3127,6 +3172,7 @@ void gl_renderer_present(const uint32_t *pixels, int src_w, int src_h, int linea
p_glActiveTexture(PSXGL_TEXTURE0);
upload_present_tex(pixels, src_w, src_h, filt_mode >= 0 ? 1 : 0);
p_glUseProgram(s_present_prog); p_glUniform1i(s_present_uTex, 0);
present_set_gamma(s_present_uGamma, 1);
present_set_sharp(filt_mode, src_w, src_h, lw, lh);
/* CPU present texture holds exactly the display rect, so v_uv spans it and
* pitch == display height == src_h. */
@@ -3961,6 +4007,7 @@ static void interp_draw_quad(float alpha, int lx, int ly, int lw, int lh) {
p_glUniform1i(s_interp_uCurr, 1);
p_glUniform1f(s_interp_uAlpha, alpha);
p_glUniform1i(s_interp_uBlendMode, s_interp_blend_mode);
present_set_gamma(s_interp_uGamma, 1);
p_glUniform4f(s_interp_uUvRect, 0.f, 0.f, 1.f, 1.f);
/* Interp textures hold exactly the display rect (uv_rect is 0..1), so pitch
* == display height == s_interp_h. */
@@ -4090,6 +4137,7 @@ static void gl_draw_osd_image(const uint32_t *px, int ow, int oh,
glViewport(vx, wh - vy - dh, dw, dh);
p_glUseProgram(s_present_prog);
p_glUniform1i(s_present_uTex, 0);
present_set_gamma(s_present_uGamma, 0);
present_set_sharp(0, 0, 0, 0, 0); /* OSD is authored at output res */
PRESENT_SCANLINE(0, 0, 0); /* never scanline the host OSD */
/* Host OSD bitmaps are top-down (row 0 = top), same as guest CPU
@@ -4182,7 +4230,8 @@ static void gl_swap_with_osd(void) {
static void present_target_quad(GLuint tex, int tex_w, int tex_h,
int x, int y, int w, int h, int linear,
int lx, int ly, int lw, int lh, int v_flip) {
int lx, int ly, int lw, int lh, int v_flip,
int apply_gamma) {
float u0, v0, u1, v1;
p_glBindFramebuffer(PSXGL_FRAMEBUFFER, 0);
glViewport(lx, ly, lw, lh);
@@ -4192,6 +4241,7 @@ static void present_target_quad(GLuint tex, int tex_w, int tex_h,
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, linear ? GL_LINEAR : GL_NEAREST);
p_glUseProgram(s_present_prog);
p_glUniform1i(s_present_uTex, 0);
present_set_gamma(s_present_uGamma, apply_gamma);
/* The rasterized path already renders at the internal scale, so it has no
* low-res source to reconstruct — keep the plain sample. */
present_set_sharp(0, 0, 0, 0, 0);
@@ -4264,6 +4314,7 @@ static void present_bezel(int ww, int wh, int lx, int ly, int lw, int lh) {
glBindTexture(GL_TEXTURE_2D, s_bezel_tex);
p_glUseProgram(s_present_prog);
p_glUniform1i(s_present_uTex, 0);
present_set_gamma(s_present_uGamma, 0);
p_glUniform4f(s_present_uUvRect, 0.0f, 0.0f, 1.0f, 1.0f);
PRESENT_SCANLINE(0, 0, 0); /* bezel art is not scanlined */
p_glBindVertexArray(s_present_vao);
@@ -4309,7 +4360,7 @@ int gl_renderer_present_hold_last(void) {
}
/* v_flip=0: drawable capture is already screen-oriented. */
present_target_quad(s_hold_tex, s_hold_tw, s_hold_th,
0, 0, s_hold_tw, s_hold_th, 0, lx, ly, lw, lh, 0);
0, 0, s_hold_tw, s_hold_th, 0, lx, ly, lw, lh, 0, 0);
} else {
if (s_hold_force_4_3)
letterbox_rect_aspect(ww, wh, 4, 3, &lx, &ly, &lw, &lh);
@@ -4317,7 +4368,7 @@ int gl_renderer_present_hold_last(void) {
letterbox_rect(ww, wh, &lx, &ly, &lw, &lh);
present_target_quad(s_hold_tex, s_hold_tw, s_hold_th,
0, 0, s_hold_tw, s_hold_th, s_hold_linear,
lx, ly, lw, lh, 1);
lx, ly, lw, lh, 1, 1);
/* Upgrade to drawable after letterboxing once. Live+interp leaves
* HOLD_NATIVE (no Swap on main); drawable path is the soak-proven
* full-window image (GL without interp). */
@@ -4382,7 +4433,7 @@ void gl_renderer_present_vram(int disp_x, int disp_y, int w, int h, int linear,
}
present_bezel(ww, wh, lx, ly, lw, lh);
present_target_quad(s_hr_tex, VRAM_W, VRAM_H,
disp_x, disp_y, w, h, linear, lx, ly, lw, lh, 1);
disp_x, disp_y, w, h, linear, lx, ly, lw, lh, 1, 1);
pres_record(GL_PRES_VRAM, disp_x, disp_y, w, h, lx, ly, lw, lh);
hold_capture_drawable();
latency_ring_mark(LAT_SWAP_BEGIN);
@@ -4486,7 +4537,7 @@ int gl_renderer_present_wide_fbo(int disp_x, int disp_y, int disp_h, int linear)
return 1;
}
present_target_quad(tex, g_wide_w, VRAM_H,
0, disp_y, g_wide_w, disp_h, linear, lx, ly, lw, lh, 1);
0, disp_y, g_wide_w, disp_h, linear, lx, ly, lw, lh, 1, 1);
pres_record(GL_PRES_WIDE, disp_x, disp_y, g_wide_w, disp_h, lx, ly, lw, lh);
hold_capture_drawable();
latency_ring_mark(LAT_SWAP_BEGIN);