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Improve matrix precision (with even more hacks!)

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This commit is contained in:
Sean Maas 2021-02-26 17:37:03 -05:00
parent 5dd241c57d
commit e528fa81b3
1 changed files with 20 additions and 5 deletions
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25
src/nds/nds_renderer.c
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@ -200,7 +200,7 @@ static void draw_vertices(const struct Vertex **v, int count) {
const m4x4 vertex = {{
PosTestXresult(), 0, 0, 0,
0, PosTestYresult(), 0, 0,
0, 0, PosTestZresult() - 3, 0,
0, 0, PosTestZresult() - (3 << 4), 0,
0, 0, 0, PosTestWresult()
}};
glLoadMatrix4x4(&vertex);
@ -259,7 +259,7 @@ static void draw_vertices(const struct Vertex **v, int count) {
const m4x4 vertex = {{
PosTestXresult(), 0, 0, 0,
0, PosTestYresult(), 0, 0,
0, 0, (--z_depth) / 6, 0,
0, 0, ((--z_depth) / 6) << 4, 0,
0, 0, 0, PosTestWresult()
}};
glLoadMatrix4x4(&vertex);
@ -440,12 +440,12 @@ static void g_geometrymode(Gwords *words) {
}
static void g_mtx(Gwords *words) {
// Load a matrix, shifting the elements so they have 12-bit fractionals for the DS
// Load a matrix with 16-bit fractionals
m4x4 matrix;
for (int i = 0; i < 16; i += 2) {
const uint32_t *data = &((uint32_t*)words->w1)[i / 2];
matrix.m[i + 0] = ((int32_t)((data[0] & 0xFFFF0000) | (data[8] >> 16)) + 8) >> 4;
matrix.m[i + 1] = ((int32_t)((data[0] << 16) | (data[8] & 0x0000FFFF)) + 8) >> 4;
matrix.m[i + 0] = (int32_t)((data[0] & 0xFFFF0000) | (data[8] >> 16));
matrix.m[i + 1] = (int32_t)((data[0] << 16) | (data[8] & 0x0000FFFF));
}
// Perform a matrix operation
@ -457,6 +457,16 @@ static void g_mtx(Gwords *words) {
if (params & G_MTX_LOAD) {
glLoadMatrix4x4(&matrix);
} else {
// To preserve some precision, the projection matrix isn't shifted to have 12-bit fractionals
// Multiplication still needs to work though, so scale the matrix before multiplying it
const m4x4 shrink = {{
1 << 8, 0, 0, 0,
0, 1 << 8, 0, 0,
0, 0, 1 << 8, 0,
0, 0, 0, 1 << 8
}};
glMultMatrix4x4(&shrink);
glMultMatrix4x4(&matrix);
}
} else {
@ -467,6 +477,11 @@ static void g_mtx(Gwords *words) {
glPushMatrix();
}
// Shift the matrix elements so they have 12-bit fractionals for the DS
for (int i = 0; i < 16; i++) {
matrix.m[i] >>= 4;
}
// Load or multiply the modelview matrix
if (params & G_MTX_LOAD) {
glLoadMatrix4x4(&matrix);