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[gl] Make perspective matrix setup consistent

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Now GL perspective matrix setup matches that of GLSL and Vulkan, and
GL's z_up matrix matches GLSL's (as it should, since they're really
going through the same API). GL also needs the depth adjustmet matrix
now. Other than having to google the docs for glFrustum, there's nothing
wrong with the function itself, but it's nice to have direct control
over the matrices.

In the process, I discovered how horribly confused I've been at times
with respect to the handedness of GL and Quake: GL is right-handed
(y-up, z-out, x-right), as is Quake itself (but z-up, y-left, x-in), but
as the perspective matrix used in the three renderers expects z-in,
having x-right and y-up makes the matrix effectively left-handed (not
for Vulkan though, because there it's y-down, x-right, z-up, so
right-handed again).
This commit is contained in:
Bill Currie 2022-03-27 13:15:15 +09:00
parent 12776e487a
commit aafd5c3d81
1 changed files with 23 additions and 22 deletions
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45
libs/video/renderer/gl/gl_rmain.c
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@ -230,38 +230,39 @@ R_DrawViewModel (void)
}
static void
MYgluPerspective (GLdouble fovy, GLdouble aspect, GLdouble zNear,
GLdouble zFar)
R_Perspective (void)
{
GLdouble xmin, xmax, ymin, ymax;
float aspect = (float) r_refdef.vrect.width / r_refdef.vrect.height;
float f = 1 / tan (r_refdef.fov_y * M_PI / 360);
float neard, fard;
mat4f_t proj;
ymax = zNear * tan (fovy * M_PI / 360.0);
ymin = -ymax;
neard = r_nearclip->value;
fard = r_farclip->value;
xmin = ymin * aspect;
xmax = -xmin;
// NOTE columns!
proj[0] = (vec4f_t) { f / aspect, 0, 0, 0 };
proj[1] = (vec4f_t) { 0, f, 0, 0 };
proj[2] = (vec4f_t) { 0, 0, (fard) / (fard - neard), 1 };
proj[3] = (vec4f_t) { 0, 0, (fard * neard) / (neard - fard), 0 };
// printf ("glFrustum (%f, %f, %f, %f)\n", xmin, xmax, ymin, ymax);
qfglFrustum (xmin, xmax, ymin, ymax, zNear, zFar);
}
static void
R_SetupGL_Viewport_and_Perspective (void)
{
float screenaspect;
// convert 0..1 depth buffer range to -1..1
static mat4f_t depth_range = {
{ 1, 0, 0, 0},
{ 0, 1, 0, 0},
{ 0, 0, 2, 0},
{ 0, 0,-1, 1},
};
mmulf (proj, depth_range, proj);
qfglMatrixMode (GL_PROJECTION);
qfglLoadIdentity ();
screenaspect = r_refdef.vrect.width / (float) r_refdef.vrect.height;
MYgluPerspective (r_refdef.fov_y, screenaspect, r_nearclip->value,
r_farclip->value);
qfglLoadMatrixf (&proj[0][0]);
}
static void
R_SetupGL (void)
{
R_SetupGL_Viewport_and_Perspective ();
R_Perspective ();
qfglFrontFace (GL_CW);
@ -269,7 +270,7 @@ R_SetupGL (void)
qfglLoadIdentity ();
static mat4f_t z_up = {
{ 0, 0, -1, 0},
{ 0, 0, 1, 0},
{-1, 0, 0, 0},
{ 0, 1, 0, 0},
{ 0, 0, 0, 1},