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TINYGL: Fix ARGBST scaling.

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I based ARGB scaling on ST scaling without giving it enough thought.
It accidentally uncovered an older bug in glopClear, which made me recheck
these formulas.
ST scaling maps [0.0, 1.0] to [0x01.0000, 0xff.0000], meaning the first and
last texture rows and columns are never shown.
Treating s and t as proportions of ST_MAX fixes this by mapping to
[0x00.0000, 0xff.fffc] (last two fractional bits being off-precision, as
there are only 14 bits), covering the whole available range.
This commit is contained in:
Vincent Pelletier 2017-05-01 08:28:55 +00:00
parent 8c1954359e
commit 4bcc95f217
3 changed files with 15 additions and 24 deletions
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16
graphics/tinygl/clip.cpp
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@ -50,14 +50,10 @@ void gl_transform_to_viewport(GLContext *c, GLVertex *v) {
v->zp.z = (int)(v->pc.Z * winv * c->viewport.scale.Z + c->viewport.trans.Z);
// color
if (c->lighting_enabled) {
v->zp.r = (int)(v->color.X * (ZB_POINT_RED_MAX - ZB_POINT_RED_MIN)
+ ZB_POINT_RED_MIN);
v->zp.g = (int)(v->color.Y * (ZB_POINT_GREEN_MAX - ZB_POINT_GREEN_MIN)
+ ZB_POINT_GREEN_MIN);
v->zp.b = (int)(v->color.Z * (ZB_POINT_BLUE_MAX - ZB_POINT_BLUE_MIN)
+ ZB_POINT_BLUE_MIN);
v->zp.a = (int)(v->color.W * (ZB_POINT_ALPHA_MAX - ZB_POINT_ALPHA_MIN)
+ ZB_POINT_ALPHA_MIN);
v->zp.r = (int)(v->color.X * ZB_POINT_RED_MAX);
v->zp.g = (int)(v->color.Y * ZB_POINT_GREEN_MAX);
v->zp.b = (int)(v->color.Z * ZB_POINT_BLUE_MAX);
v->zp.a = (int)(v->color.W * ZB_POINT_ALPHA_MAX);
} else {
// no need to convert to integer if no lighting : take current color
v->zp.r = c->longcurrent_color[0];
@ -68,8 +64,8 @@ void gl_transform_to_viewport(GLContext *c, GLVertex *v) {
// texture
if (c->texture_2d_enabled) {
v->zp.s = (int)(v->tex_coord.X * (ZB_POINT_ST_MAX - ZB_POINT_ST_MIN) + ZB_POINT_ST_MIN);
v->zp.t = (int)(v->tex_coord.Y * (ZB_POINT_ST_MAX - ZB_POINT_ST_MIN) + ZB_POINT_ST_MIN);
v->zp.s = (int)(v->tex_coord.X * ZB_POINT_ST_MAX);
v->zp.t = (int)(v->tex_coord.Y * ZB_POINT_ST_MAX);
}
}