diff options
| -rw-r--r-- | src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp | 201 |
1 files changed, 182 insertions, 19 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 7a5f9834423..d571ecd4394 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) { @@ -144,28 +156,179 @@ lower_texture_grad_visitor::visit_leave(ir_texture *ir) new(mem_ctx) ir_variable(grad_type, "dPdy", ir_var_temporary); emit(dPdy, mul(size, ir->lod_info.grad.dPdy)); - /* Calculate rho from equation 3.20 of the GL 3.0 specification. */ - ir_rvalue *rho; - if (dPdx->type->is_scalar()) { - rho = expr(ir_binop_max, expr(ir_unop_abs, dPdx), - expr(ir_unop_abs, dPdy)); - } else { - rho = expr(ir_binop_max, expr(ir_unop_sqrt, dot(dPdx, dPdx)), - expr(ir_unop_sqrt, dot(dPdy, dPdy))); - } - - /* lambda_base = log2(rho). We're ignoring GL state biases for now. - * - * For cube maps the result of these formulas is giving us a value of rho - * that is twice the value we should use, so divide it by 2 or, - * alternatively, remove one unit from the result of the log2 computation. - */ 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::vec2_type, "dx"); + ir_variable *dy = temp(mem_ctx, glsl_type::vec2_type, "dy"); + + /* tmp = Q.xy * recip; + * dx = recip * ( dQdx.xy - (tmp * dQdx.z) ); + * dy = recip * ( dQdy.xy - (tmp * dQdy.z) ); + */ + ir_variable *tmp = temp(mem_ctx, glsl_type::vec2_type, "tmp"); + EMIT(assign(tmp, mul(swizzle_xy(Q), recip))); + EMIT(assign(dx, mul(recip, sub(swizzle_xy(dQdx), + mul(tmp, swizzle_z(dQdx)))))); + EMIT(assign(dy, mul(recip, sub(swizzle_xy(dQdy), + mul(tmp, swizzle_z(dQdy)))))); + + /* 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 { + /* Calculate rho from equation 3.20 of the GL 3.0 specification. */ + ir_rvalue *rho; + if (dPdx->type->is_scalar()) { + rho = expr(ir_binop_max, expr(ir_unop_abs, dPdx), + expr(ir_unop_abs, dPdy)); + } else { + rho = expr(ir_binop_max, expr(ir_unop_sqrt, dot(dPdx, dPdx)), + expr(ir_unop_sqrt, dot(dPdy, dPdy))); + } + + /* lambda_base = log2(rho). We're ignoring GL state biases for now. */ ir->lod_info.lod = expr(ir_unop_log2, rho); } |