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add fog to GL1.3 renderer 

uses two different methods, with the first one taking priority if it's available:

a) use the fog factor supplied in the fog colors as a GL_FOG_COORD; GL_FOG_COORD is only available in GL1.4+ or when GL_EXT_fog_coord is present

just blend the same triangles a second time, but replace the color with fog color and multiply the alpha by fog alpha
This commit is contained in:
fgsfds 2020-05-21 03:12:51 +03:00
parent 2714708ca9
commit 0724f0ed09
1 changed files with 96 additions and 11 deletions
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107
src/pc/gfx/gfx_opengl_legacy.c
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@ -25,6 +25,21 @@
#define GL_GLEXT_PROTOTYPES 1
#include <SDL2/SDL_opengl.h>
// redefine this if using a different GL loader
#define mglGetProcAddress(name) SDL_GL_GetProcAddress(name)
// we'll define and load it manually in init, just in case
typedef void (*PFNMGLFOGCOORDPOINTERPROC)(GLenum type, GLsizei stride, const void *pointer);
static PFNMGLFOGCOORDPOINTERPROC mglFogCoordPointer = NULL;
// since these can have different names, might as well redefine them to a single one
#undef GL_FOG_COORD_SRC
#undef GL_FOG_COORD
#undef GL_FOG_COORD_ARRAY
#define GL_FOG_COORD_SRC 0x8450
#define GL_FOG_COORD 0x8451
#define GL_FOG_COORD_ARRAY 0x8457
#include "gfx_cc.h"
#include "gfx_rendering_api.h"
#include "macros.h"
@ -65,9 +80,12 @@ static uint8_t shader_program_pool_size;
static struct ShaderProgram *cur_shader = NULL;
static const float *cur_buf = NULL;
static const float *cur_fog_ofs = NULL;
static size_t cur_buf_size = 0;
static size_t cur_buf_num_tris = 0;
static size_t cur_buf_stride = 0;
static bool gl_blend = false;
static bool gl_adv_fog = false;
static const float c_white[] = { 1.f, 1.f, 1.f, 1.f };
@ -186,13 +204,18 @@ static void gfx_opengl_apply_shader(struct ShaderProgram *prg) {
}
if (prg->shader_id & SHADER_OPT_FOG) {
// have fog, but fog colors are the same for every vertex
// TODO: alpha ain't the same, maybe use glSecondaryColorPointer?
// TODO: or pass start and end from gsSPFogPosition somehow or calculate them from z0, w0 and a0?
// TODO: or alpha blend solid triangles on top, using the fog factor as alpha
// glEnable(GL_FOG);
// glFogi(GL_FOG_MODE, GL_LINEAR);
// glFogfv(GL_FOG_COLOR, ofs);
// fog requested, we can deal with it in one of two ways
if (gl_adv_fog) {
// if GL_EXT_fog_coord is available, use the provided fog factor as scaled depth for GL fog
const float fogrgb[] = { ofs[0], ofs[1], ofs[2] };
glEnable(GL_FOG);
glFogfv(GL_FOG_COLOR, fogrgb); // color is the same for all verts, only intensity is different
glEnableClientState(GL_FOG_COORD_ARRAY);
mglFogCoordPointer(GL_FLOAT, cur_buf_stride, ofs + 3); // point it to alpha, which is fog factor
} else {
// if there's no fog coords available, blend it on top of normal tris later
cur_fog_ofs = ofs;
}
ofs += 4;
}
@ -251,8 +274,11 @@ static void gfx_opengl_unload_shader(struct ShaderProgram *old_prg) {
glDisable(GL_TEXTURE0);
glDisable(GL_TEXTURE_2D);
glDisable(GL_ALPHA_TEST);
glDisable(GL_FOG);
cur_fog_ofs = NULL; // clear fog colors
glDisableClientState(GL_COLOR_ARRAY);
if (gl_adv_fog) glDisableClientState(GL_FOG_COORD_ARRAY);
}
static void gfx_opengl_load_shader(struct ShaderProgram *new_prg) {
@ -401,6 +427,7 @@ static void gfx_opengl_set_scissor(int x, int y, int width, int height) {
}
static void gfx_opengl_set_use_alpha(bool use_alpha) {
gl_blend = use_alpha;
if (use_alpha) {
glEnable(GL_BLEND);
} else {
@ -408,6 +435,32 @@ static void gfx_opengl_set_use_alpha(bool use_alpha) {
}
}
// draws the same triangles as plain fog color + fog intensity as alpha
// on top of the normal tris and blends them to achieve sort of the same effect
// as fog would
static inline void gfx_opengl_blend_fog_tris(void) {
// if a texture was used, replace it with fog color instead, but still keep the alpha
if (cur_shader->texture_used[0]) {
glActiveTexture(GL_TEXTURE0);
TEXENV_COMBINE_ON();
// out.rgb = input0.rgb
TEXENV_COMBINE_SET1(RGB, GL_REPLACE, GL_PRIMARY_COLOR);
// out.a = texel0.a * input0.a
TEXENV_COMBINE_SET2(ALPHA, GL_MODULATE, GL_TEXTURE, GL_PRIMARY_COLOR);
}
glEnableClientState(GL_COLOR_ARRAY); // enable color array temporarily
glColorPointer(4, GL_FLOAT, cur_buf_stride, cur_fog_ofs); // set fog colors as primary colors
if (!gl_blend) glEnable(GL_BLEND); // enable blending temporarily
glDepthFunc(GL_LEQUAL); // Z is the same as the base triangles
glDrawArrays(GL_TRIANGLES, 0, 3 * cur_buf_num_tris);
glDepthFunc(GL_LESS); // set back to default
if (!gl_blend) glDisable(GL_BLEND); // disable blending if it was disabled
glDisableClientState(GL_COLOR_ARRAY); // will get reenabled later anyway
}
static void gfx_opengl_draw_triangles(float buf_vbo[], size_t buf_vbo_len, size_t buf_vbo_num_tris) {
//printf("flushing %d tris\n", buf_vbo_num_tris);
@ -418,7 +471,10 @@ static void gfx_opengl_draw_triangles(float buf_vbo[], size_t buf_vbo_len, size_
gfx_opengl_apply_shader(cur_shader);
glDrawArrays(GL_TRIANGLES, 0, 3 * buf_vbo_num_tris);
glDrawArrays(GL_TRIANGLES, 0, 3 * cur_buf_num_tris);
// cur_fog_ofs is only set if GL_EXT_fog_coord isn't used
if (cur_fog_ofs) gfx_opengl_blend_fog_tris();
}
static inline bool gl_check_ext(const char *name) {
@ -428,10 +484,11 @@ static inline bool gl_check_ext(const char *name) {
extstr = (const char *)glGetString(GL_EXTENSIONS);
if (!strstr(extstr, name)) {
fprintf(stderr, "Required GL extension not supported: %s\n", name);
fprintf(stderr, "GL extension not supported: %s\n", name);
return false;
}
printf("GL extension detected: %s\n", name);
return true;
}
@ -465,16 +522,44 @@ static void gfx_opengl_init(void) {
}
// check extensions that we need
bool supported =
const bool supported =
gl_check_ext("GL_ARB_multitexture") &&
gl_check_ext("GL_ARB_texture_env_combine");
if (!supported) abort();
gl_adv_fog = false;
// check whether we can use advanced fog shit
const bool fog_ext =
vmajor > 1 || vminor > 3 ||
gl_check_ext("GL_EXT_fog_coord") ||
gl_check_ext("GL_ARB_fog_coord");
if (fog_ext) {
// try to load manually, as this might be an extension, and even then the ext list may lie
mglFogCoordPointer = mglGetProcAddress("glFogCoordPointer");
if (!mglFogCoordPointer) mglFogCoordPointer = mglGetProcAddress("glFogCoordPointerEXT");
if (!mglFogCoordPointer) mglFogCoordPointer = mglGetProcAddress("glFogCoordPointerARB");
if (!mglFogCoordPointer)
printf("glFogCoordPointer is not actually available, it won't be used.\n");
else
gl_adv_fog = true; // appears to be all good
}
printf("GL_VERSION = %s\n", glGetString(GL_VERSION));
printf("GL_EXTENSIONS =\n%s\n", glGetString(GL_EXTENSIONS));
// these never change
if (gl_adv_fog) {
// set fog params, they never change
printf("GL_EXT_fog_coord available, using that for fog\n");
glFogi(GL_FOG_COORD_SRC, GL_FOG_COORD);
glFogi(GL_FOG_MODE, GL_LINEAR);
glFogf(GL_FOG_START, 0.0f);
glFogf(GL_FOG_END, 1.0f);
}
// these also never change
glEnableClientState(GL_VERTEX_ARRAY);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, c_white);