Hi Tapani, Kevin, awesome work! I was curious about how to fix this, at least when I was looking at the specs for this stuff it was not obvious that the Math involved for this was so different, I only recall seeing the reference that texure coordinates had to be normalized to a [-1, 1] space after selecting the face in the cube, but I did not see formulas to implement all this like they had for the normal case. It looks like the Math involved is quite different.
I added some minor comments below: On Thu, 2015-09-17 at 08:12 +0300, Tapani Pälli wrote: > 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.pa...@intel.com> > Signed-off-by: Kevin Rogovin <kevin.rogo...@intel.com> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91114 > Cc: "11.0 10.7" <mesa-sta...@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)); It seems that in this case we don't need rho at all, so we should probably move the rho computation to the else branch entirely. > + /* 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: Great comment! Where did you get this from? Is this detailed somwhere in the spec? In that case maybe we want to add a reference to that as well. > + 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; > + } This is a nitpick: you use 'Q, dQdx and dQdy' above, and 'q, dqdx, dqdy' below... you probably want to be consistent with the capitalization and use Q everywhere, since that is what you use in the actual implementation. > + 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) ^ Remove this blank space here > + = -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)))) ^^^^^^ 'L' instead of 'l' > + = -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)); Maybe you want to use 'M' instead of 'm' for consistency. > + L = textureSize(sampler, 0).x; Is it always going to be .x (the width) that we need here? > + result = -1.0 + 0.5 * log2(l * l * m); ^^^^^^ 'L' instead of 'l' > + */ > + > +/* 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); Isn't that 0 on the 4th component actually the same as SWIZZLE_X? I suppose that you just want to make clear that we don't care about that component... in that case, could we use something like SWIZZLE_NIL instead? If not I guess 0 is good enough. > + 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"); I think we usually use glsl_type::vec2_type instead of the glsl_type::vec(components) version? > + /* 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)))))); What if, instead of q.xy * (dqdx.z * recip), we do (q.xy * recip) * dqdx.z? In that case the (q.xy * recip) can be emitted only once and its result reused for both EMITs. Iago > + /* 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); > } _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
