[Mesa-stable] [PATCH] i965: fix textureGrad for cubemaps
Tapani Pälli
tapani.palli at intel.com
Wed Sep 16 22:12:08 PDT 2015
Fixes regression caused by commit
2b1cdb0eddb73f62e4848d4b64840067f1f70865 in:
ES3-CTS.gtf.GL3Tests.shadow.shadow_execution_frag
No regressions observed in deqp, CTS or Piglit.
Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
Signed-off-by: Kevin Rogovin <kevin.rogovin at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91114
Cc: "11.0 10.7" <mesa-stable at lists.freedesktop.org>
---
.../dri/i965/brw_lower_texture_gradients.cpp | 172 ++++++++++++++++++++-
1 file changed, 169 insertions(+), 3 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp b/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
index 7a5f983..f8a31b7 100644
--- a/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
+++ b/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
@@ -48,6 +48,7 @@ public:
private:
void emit(ir_variable *, ir_rvalue *);
+ ir_variable *temp(void *ctx, const glsl_type *type, const char *name);
};
/**
@@ -60,6 +61,17 @@ lower_texture_grad_visitor::emit(ir_variable *var, ir_rvalue *value)
base_ir->insert_before(assign(var, value));
}
+/**
+ * Emit a temporary variable declaration
+ */
+ir_variable *
+lower_texture_grad_visitor::temp(void *ctx, const glsl_type *type, const char *name)
+{
+ ir_variable *var = new(ctx) ir_variable(type, name, ir_var_temporary);
+ base_ir->insert_before(var);
+ return var;
+}
+
static const glsl_type *
txs_type(const glsl_type *type)
{
@@ -162,9 +174,163 @@ lower_texture_grad_visitor::visit_leave(ir_texture *ir)
*/
ir->op = ir_txl;
if (ir->sampler->type->sampler_dimensionality == GLSL_SAMPLER_DIM_CUBE) {
- ir->lod_info.lod = expr(ir_binop_add,
- expr(ir_unop_log2, rho),
- new(mem_ctx) ir_constant(-1.0f));
+ /* Cubemap texture lookups first generate a texture coordinate normalized
+ to [-1, 1] on the appropiate face. The appropiate face is determined
+ by which component has largest magnitude and its sign. The texture
+ coordinate is the quotient of the remaining texture coordinates against
+ that absolute value of the component of largest magnitude. This division
+ requires that the computing of the derivative of the texel coordinate
+ must use the quotient rule. The high level GLSL code is as follows:
+
+ Step 1: selection
+
+ vec3 abs_p, Q, dQdx, dQdy;
+ abs_p = abs(ir->coordinate);
+ if (abs_p.x >= max(abs_p.y, abs_p.z)) {
+ Q = ir->coordinate.yzx;
+ dQdx = ir->lod_info.grad.dPdx.yzx;
+ dQdy = ir->lod_info.grad.dPdy.yzx;
+ }
+ if (abs_p.y >= max(abs_p.x, abs_p.z)) {
+ Q = ir->coordinate.xzy;
+ dQdx = ir->lod_info.grad.dPdx.xzy;
+ dQdy = ir->lod_info.grad.dPdy.xzy;
+ }
+ if (abs_p.z >= max(abs_p.x, abs_p.y)) {
+ Q = ir->coordinate;
+ dQdx = ir->lod_info.grad.dPdx;
+ dQdy = ir->lod_info.grad.dPdy;
+ }
+
+ Step 2: use quotient rule to compute derivative. The normalized to [-1, 1]
+ texel coordinate is given by Q.xy / (sign(Q.z) * Q.z). We are only concerned
+ with the magnitudes of the derivatives whose values are not affected by the
+ sign. We drop the sign from the computation.
+
+ vec2 dx, dy;
+ float recip;
+
+ recip = 1.0 / Q.z;
+ dx = recip * ( dqdx.xy - q.xy * (dqdx.z * recip) );
+ dy = recip * ( dqdy.xy - q.xy * (dqdy.z * recip) );
+
+ Step 3: compute LOD. At this point we have the derivatives of the
+ texture coordinates normalized to [-1,1]. We take the LOD to be
+ result = log2( max(sqrt(dot(dx, dx)), sqrt(dy, dy)) * 0.5 * L)
+ = -1.0 + log2(max(sqrt(dot(dx, dx)), sqrt(dy, dy)) * L)
+ = -1.0 + log2(sqrt(max(dot(dx, dx), dot(dy,dy))) * L)
+ = -1.0 + log2(sqrt(l * l * max(dot(dx, dx), dot(dy,dy))))
+ = -1.0 + 0.5 * log2(L * L * max(dot(dx, dx), dot(dy,dy)))
+ where L is the dimension of the cubemap. The code is:
+
+ float m, result;
+ m = max(dot(dx, dx), dot(dy, dy));
+ L = textureSize(sampler, 0).x;
+ result = -1.0 + 0.5 * log2(l * l * m);
+ */
+
+/* Helpers to make code more human readable. */
+#define EMIT(instr) base_ir->insert_before(instr)
+#define THEN(irif, instr) irif->then_instructions.push_tail(instr)
+#define CLONE(x) x->clone(mem_ctx, NULL)
+
+ ir_variable *abs_p = temp(mem_ctx, glsl_type::vec3_type, "abs_p");
+
+ EMIT(assign(abs_p, swizzle_for_size(abs(CLONE(ir->coordinate)), 3)));
+
+ ir_variable *Q = temp(mem_ctx, glsl_type::vec3_type, "Q");
+ ir_variable *dQdx = temp(mem_ctx, glsl_type::vec3_type, "dQdx");
+ ir_variable *dQdy = temp(mem_ctx, glsl_type::vec3_type, "dQdy");
+
+ /* unmodified dPdx, dPdy values */
+ ir_rvalue *dPdx = ir->lod_info.grad.dPdx;
+ ir_rvalue *dPdy = ir->lod_info.grad.dPdy;
+
+ /* 1. compute selector */
+
+ /* if (abs_p.x >= max(abs_p.y, abs_p.z)) ... */
+ ir_if *branch_x =
+ new(mem_ctx) ir_if(gequal(swizzle_x(abs_p),
+ max2(swizzle_y(abs_p), swizzle_z(abs_p))));
+
+ /* q = p.yzx;
+ * dqdx = dpdx.yzx;
+ * dqdy = dpdy.yzx;
+ */
+ int yzx = MAKE_SWIZZLE4(SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X, 0);
+ THEN(branch_x, assign(Q, swizzle(CLONE(ir->coordinate), yzx, 3)));
+ THEN(branch_x, assign(dQdx, swizzle(CLONE(dPdx), yzx, 3)));
+ THEN(branch_x, assign(dQdy, swizzle(CLONE(dPdy), yzx, 3)));
+ EMIT(branch_x);
+
+ /* if (abs_p.y >= max(abs_p.x, abs_p.z)) */
+ ir_if *branch_y =
+ new(mem_ctx) ir_if(gequal(swizzle_y(abs_p),
+ max2(swizzle_x(abs_p), swizzle_z(abs_p))));
+
+ /* q = p.xzy;
+ * dqdx = dpdx.xzy;
+ * dqdy = dpdy.xzy;
+ */
+ int xzy = MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_Z, SWIZZLE_Y, 0);
+ THEN(branch_y, assign(Q, swizzle(CLONE(ir->coordinate), xzy, 3)));
+ THEN(branch_y, assign(dQdx, swizzle(CLONE(dPdx), xzy, 3)));
+ THEN(branch_y, assign(dQdy, swizzle(CLONE(dPdy), xzy, 3)));
+ EMIT(branch_y);
+
+ /* if (abs_p.z >= max(abs_p.x, abs_p.y)) */
+ ir_if *branch_z =
+ new(mem_ctx) ir_if(gequal(swizzle_z(abs_p),
+ max2(swizzle_x(abs_p), swizzle_y(abs_p))));
+
+ /* q = p;
+ * dqdx = dpdx;
+ * dqdy = dpdy;
+ */
+ THEN(branch_z, assign(Q, swizzle_for_size(CLONE(ir->coordinate), 3)));
+ THEN(branch_z, assign(dQdx, CLONE(dPdx)));
+ THEN(branch_z, assign(dQdy, CLONE(dPdy)));
+ EMIT(branch_z);
+
+ /* 2. quotient rule */
+ ir_variable *recip = temp(mem_ctx, glsl_type::float_type, "recip");
+ EMIT(assign(recip, div(new(mem_ctx) ir_constant(1.0f), swizzle_z(Q))));
+
+ ir_variable *dx = temp(mem_ctx, glsl_type::vec(2), "dx");
+ ir_variable *dy = temp(mem_ctx, glsl_type::vec(2), "dy");
+
+ /* dx = recip * ( dqdx.xy - q.xy * (dqdx.z * recip) );
+ * dy = recip * ( dqdy.xy - q.xy * (dqdy.z * recip) );
+ */
+ EMIT(assign(dx, mul(recip, sub(swizzle_xy(dQdx),
+ mul(swizzle_xy(Q), mul(swizzle_z(dQdx),
+ recip))))));
+ EMIT(assign(dy, mul(recip, sub(swizzle_xy(dQdy),
+ mul(swizzle_xy(Q), mul(swizzle_z(dQdy),
+ recip))))));
+
+ /* m = max(dot(dx, dx), dot(dy, dy)); */
+ ir_variable *M = temp(mem_ctx, glsl_type::float_type, "m");
+ EMIT(assign(M, max2(dot(dx, dx), dot(dy, dy))));
+
+ /* size has textureSize() of LOD 0 */
+ ir_variable *L = temp(mem_ctx, glsl_type::float_type, "L");
+ EMIT(assign(L, swizzle_x(size)));
+
+ ir_variable *result = temp(mem_ctx, glsl_type::float_type, "result");
+
+ /* result = -1.0 + 0.5 * log2(L * L * m); */
+ EMIT(assign(result,
+ add(new(mem_ctx)ir_constant(-1.0f),
+ mul(new(mem_ctx)ir_constant(0.5f),
+ expr(ir_unop_log2, mul(mul(L, L), M))))));
+
+ /* 3. final assignment of parameters to textureLod call */
+ ir->lod_info.lod = new (mem_ctx) ir_dereference_variable(result);
+
+#undef THEN
+#undef EMIT
+
} else {
ir->lod_info.lod = expr(ir_unop_log2, rho);
}
--
2.4.3
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