[PATCH 8/9] intel gen4-5: Make noperspective clipping work.

Olivier Galibert
2012-07-19T20:00:23Z

At this point all interpolation tests with fixed clipping work.

Signed-off-by: Olivier Galibert <galibert@pobox.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
---
src/mesa/drivers/dri/i965/brw_clip.c | 9 ++
src/mesa/drivers/dri/i965/brw_clip.h | 1 +
src/mesa/drivers/dri/i965/brw_clip_util.c | 147 ++++++++++++++++++++++++++---
3 files changed, 146 insertions(+), 11 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_clip.c b/src/mesa/drivers/dri/i965/brw_clip.c
index 8512172..eca2844 100644
--- a/src/mesa/drivers/dri/i965/brw_clip.c
+++ b/src/mesa/drivers/dri/i965/brw_clip.c
@@ -239,6 +239,15 @@ brw_upload_clip_prog(struct brw_context *brw)
break;
}
}
+ key.has_noperspective_shading = 0;
+ for (i = 0; i < BRW_VERT_RESULT_MAX; i++) {
+ if (brw->interpolation_mode[i] == INTERP_QUALIFIER_NOPERSPECTIVE &&
+ brw->vs.prog_data->vue_map.slot_to_vert_result[i] != VERT_RESULT_HPOS) {
+ key.has_noperspective_shading = 1;
+ break;
+ }
+ }
+
key.pv_first = (ctx->Light.ProvokingVertex == GL_FIRST_VERTEX_CONVENTION);

memcpy(key.interpolation_mode, brw->interpolation_mode, BRW_VERT_RESULT_MAX);
diff --git a/src/mesa/drivers/dri/i965/brw_clip.h b/src/mesa/drivers/dri/i965/brw_clip.h
index 3ad2e13..66dd928 100644
--- a/src/mesa/drivers/dri/i965/brw_clip.h
+++ b/src/mesa/drivers/dri/i965/brw_clip.h
@@ -47,6 +47,7 @@ struct brw_clip_prog_key {
GLuint primitive:4;
GLuint nr_userclip:4;
GLuint has_flat_shading:1;
+ GLuint has_noperspective_shading:1;
GLuint pv_first:1;
GLuint do_unfilled:1;
GLuint fill_cw:2; /* includes cull information */
diff --git a/src/mesa/drivers/dri/i965/brw_clip_util.c b/src/mesa/drivers/dri/i965/brw_clip_util.c
index 692573e..b06ad1d 100644
--- a/src/mesa/drivers/dri/i965/brw_clip_util.c
+++ b/src/mesa/drivers/dri/i965/brw_clip_util.c
@@ -129,6 +129,8 @@ static void brw_clip_project_vertex( struct brw_clip_compile *c,

/* Interpolate between two vertices and put the result into a0.0.
* Increment a0.0 accordingly.
+ *
+ * Beware that dest_ptr can be equal to v0_ptr.
*/
void brw_clip_interp_vertex( struct brw_clip_compile *c,
struct brw_indirect dest_ptr,
@@ -138,7 +140,8 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
bool force_edgeflag)
{
struct brw_compile *p = &c->func;
- struct brw_reg tmp = get_tmp(c);
+ struct brw_context *brw = p->brw;
+ struct brw_reg t_nopersp, v0_ndc_copy;
GLuint slot;

/* Just copy the vertex header:
@@ -148,13 +151,130 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
* back on Ironlake, so needn't change it
*/
brw_copy_indirect_to_indirect(p, dest_ptr, v0_ptr, 1);
-
- /* Iterate over each attribute (could be done in pairs?)
+
+ /*
+ * First handle the 3D and NDC positioning, in case we need
+ * noperspective interpolation. Doing it early has no performance
+ * impact in any case.
+ */
+
+ /* Start by picking up the v0 NDC coordinates, because that vertex
+ * may be shared with the destination.
+ */
+ if (c->key.has_noperspective_shading) {
+ GLuint offset = brw_vert_result_to_offset(&c->vue_map,
+ BRW_VERT_RESULT_NDC);
+ v0_ndc_copy = get_tmp(c);
+ brw_MOV(p, v0_ndc_copy, deref_4f(v0_ptr, offset));
+ }
+
+ /*
+ * Compute the new 3D position
+ *
+ * dest_hpos = v0_hpos * (1 - t0) + v1_hpos * t0
+ */
+ {
+ GLuint delta = brw_vert_result_to_offset(&c->vue_map, VERT_RESULT_HPOS);
+ struct brw_reg tmp = get_tmp(c);
+ brw_MUL(p,
+ vec4(brw_null_reg()),
+ deref_4f(v1_ptr, delta),
+ t0);
+
+ brw_MAC(p,
+ tmp,
+ negate(deref_4f(v0_ptr, delta)),
+ t0);
+
+ brw_ADD(p,
+ deref_4f(dest_ptr, delta),
+ deref_4f(v0_ptr, delta),
+ tmp);
+ release_tmp(c, tmp);
+ }
+
+ /* Then recreate the projected (NDC) coordinate in the new vertex
+ * header
+ */
+ brw_clip_project_vertex(c, dest_ptr);
+
+ /*
+ * If we have noperspective attributes, we now need to compute the
+ * screen-space t.
+ */
+ if (c->key.has_noperspective_shading) {
+ GLuint delta = brw_vert_result_to_offset(&c->vue_map, BRW_VERT_RESULT_NDC);
+ struct brw_reg tmp = get_tmp(c);
+ t_nopersp = get_tmp(c);
+
+ /* Build a register with coordinates from the second and new vertices
+ *
+ * t_nopersp = vec4(v1.xy, dest.xy)
+ */
+ brw_MOV(p, t_nopersp, deref_4f(v1_ptr, delta));
+ brw_MOV(p, tmp, deref_4f(dest_ptr, delta));
+ brw_set_access_mode(p, BRW_ALIGN_16);
+ brw_MOV(p,
+ brw_writemask(t_nopersp, WRITEMASK_ZW),
+ brw_swizzle(tmp, 0,1,0,1));
+
+ /* Subtract the coordinates of the first vertex
+ *
+ * t_nopersp = vec4(v1.xy, dest.xy) - v0.xyxy
+ */
+ brw_ADD(p, t_nopersp, t_nopersp, negate(brw_swizzle(v0_ndc_copy, 0,1,0,1)));
+
+ /* Add the absolute value of the X and Y deltas so that if the
+ * points aren't in the same place on the screen we get non-zero
+ * values to divide.
+ *
+ * After that we have vert1-vert0 in t_nopersp.x and vertnew-vert0 in t_nopersp.y.
+ *
+ * t_nopersp = vec2(|v1.x -v0.x| + |v1.y -v0.y|,
+ * |dest.x-v0.x| + |dest.y-v0.y|)
+ */
+ brw_ADD(p,
+ brw_writemask(t_nopersp, WRITEMASK_XY),
+ brw_abs(brw_swizzle(t_nopersp, 0,2,0,0)),
+ brw_abs(brw_swizzle(t_nopersp, 1,3,0,0)));
+ brw_set_access_mode(p, BRW_ALIGN_1);
+
+ /* If the points are in the same place (vert1-vert0 == 0), just
+ * substitute a value that will ensure that we don't divide by
+ * 0.
+ */
+ brw_CMP(p, vec1(brw_null_reg()), BRW_CONDITIONAL_EQ,
+ vec1(t_nopersp),
+ brw_imm_f(0));
+ brw_IF(p, BRW_EXECUTE_1);
+ brw_MOV(p, t_nopersp, brw_imm_vf4(VF_ONE, VF_ZERO, VF_ZERO, VF_ZERO));
+ brw_ENDIF(p);
+
+ /* Now compute t_nopersp = t_nopersp.y/t_nopersp.x and broadcast it */
+ brw_math_invert(p, get_element(t_nopersp, 0), get_element(t_nopersp, 0));
+ brw_MUL(p,
+ vec1(t_nopersp),
+ vec1(t_nopersp),
+ vec1(suboffset(t_nopersp, 1)));
+ brw_set_access_mode(p, BRW_ALIGN_16);
+ brw_MOV(p, t_nopersp, brw_swizzle(t_nopersp, 0,0,0,0));
+ brw_set_access_mode(p, BRW_ALIGN_1);
+
+ release_tmp(c, tmp);
+ release_tmp(c, v0_ndc_copy);
+ }
+
+ /* Now we can iterate over each attribute
+ * (could be done in pairs?)
*/
for (slot = 0; slot < c->vue_map.num_slots; slot++) {
int vert_result = c->vue_map.slot_to_vert_result[slot];
GLuint delta = brw_vue_slot_to_offset(slot);

+ /* HPOS is already handled */
+ if(vert_result == VERT_RESULT_HPOS)
+ continue;
+
if (vert_result == VERT_RESULT_EDGE) {
if (force_edgeflag)
brw_MOV(p, deref_4f(dest_ptr, delta), brw_imm_f(1));
@@ -174,20 +294,29 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
*
* New = attr0 + t*attr1 - t*attr0
*/
+
+ struct brw_reg tmp = get_tmp(c);
+
+ struct brw_reg t =
+ brw->interpolation_mode[slot] == INTERP_QUALIFIER_NOPERSPECTIVE ?
+ t_nopersp : t0;
+
brw_MUL(p,
vec4(brw_null_reg()),
deref_4f(v1_ptr, delta),
- t0);
+ t);

brw_MAC(p,
tmp,
negate(deref_4f(v0_ptr, delta)),
- t0);
+ t);

brw_ADD(p,
deref_4f(dest_ptr, delta),
deref_4f(v0_ptr, delta),
tmp);
+
+ release_tmp(c, tmp);
}
}

@@ -197,12 +326,8 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
brw_MOV(p, deref_4f(dest_ptr, delta), brw_imm_f(0));
}

- release_tmp(c, tmp);
-
- /* Recreate the projected (NDC) coordinate in the new vertex
- * header:
- */
- brw_clip_project_vertex(c, dest_ptr );
+ if (c->key.has_noperspective_shading)
+ release_tmp(c, t_nopersp);
}

void brw_clip_emit_vue(struct brw_clip_compile *c,
--
1.7.10.280.gaa39