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Added two-sided polygon flag and back-face culling to Model 3 video emulation [Naibo Zhang]

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From: naibo zhang [naibo_zhang@hotmail.com]
Sent: Tuesday, October 13, 2009 6:11 PM
To: submit@mamedev.org
Subject: Sega Model-3 backface culling & stepstag rename

Sega Model-3 video emulation improvement: figured out the flag bit indicating a single-/double-side polygon. Added backface culling code. Some graphic flickering glitches are gone.
This commit is contained in:
Phil Bennett 2009-10-21 18:18:54 +00:00
parent 4e0c48083f
commit c089acef32
1 changed files with 56 additions and 44 deletions
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16
src/mame/video/model3.c
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@ -1124,7 +1124,7 @@ static void draw_model(UINT32 addr)
UINT32 *model = (addr >= 0x100000) ? &model3_vrom[addr] : &polygon_ram[addr];
UINT32 header[7];
int index = 0;
int last_polygon = FALSE;
int last_polygon = FALSE, back_face = FALSE;
int num_vertices;
int i, v, vi;
float fixed_point_fraction;
@ -1216,7 +1216,7 @@ static void draw_model(UINT32 addr)
sn[1] *= coordinate_system[1][2];
sn[2] *= coordinate_system[2][0];
/* TODO: backface culling */
/* TODO: depth bias */
/* transform vertices */
for (i = 0; i < num_vertices; i++)
{
@ -1245,6 +1245,17 @@ static void draw_model(UINT32 addr)
num_vertices = clip_polygon(clip_vert, num_vertices, clip_plane[3], clip_vert);
num_vertices = clip_polygon(clip_vert, num_vertices, clip_plane[4], clip_vert);
/* backface culling */
if( (header[6] & 0x800000) && (!(header[1] & 0x0010)) ) {
if(sn[0]*clip_vert[0].x + sn[1]*clip_vert[0].y + sn[2]*clip_vert[0].pz >0)
back_face = 1;
else
back_face = 0;
}
else
back_face = 0; //no culling for transparent or two-sided polygons
if(!back_face) {
/* homogeneous Z-divide, screen-space transformation */
for(i=0; i < num_vertices; i++) {
float ooz = 1.0f / clip_vert[i].pz;
@ -1295,6 +1306,7 @@ static void draw_model(UINT32 addr)
render_one(&tri);
}
}
++polynum;
};