1/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2  * This Source Code Form is subject to the terms of the Mozilla Public
3  * License, v. 2.0. If a copy of the MPL was not distributed with this
4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5
6Texture2D InputTexture : register(t0);
7SamplerState InputSampler : register(s0);
8Texture2D GradientTexture : register(t1);
9SamplerState GradientSampler : register(s1);
10
11cbuffer constants : register(b0)
12{
13    // Precalculate as much as we can!
14    float3 diff : packoffset(c0.x);
15    float2 center1 : packoffset(c1.x);
16    float A : packoffset(c1.z);
17    float radius1 : packoffset(c1.w);
18    float sq_radius1 : packoffset(c2.x);
19
20    // The next two values are used for a hack to compensate for an apparent
21    // bug in D2D where the GradientSampler SamplerState doesn't get the
22    // correct addressing modes.
23    float repeat_correct : packoffset(c2.y);
24    float allow_odd : packoffset(c2.z);
25
26    float3x2 transform : packoffset(c3.x);
27}
28
29float4 SampleRadialGradientPS(
30    float4 clipSpaceOutput  : SV_POSITION,
31    float4 sceneSpaceOutput : SCENE_POSITION,
32    float4 texelSpaceInput0 : TEXCOORD0
33    ) : SV_Target
34{
35  // Radial gradient painting is defined as the set of circles whose centers
36  // are described by C(t) = (C2 - C1) * t + C1; with radii
37  // R(t) = (R2 - R1) * t + R1; for R(t) > 0. This shader solves the
38  // quadratic equation that arises when calculating t for pixel (x, y).
39  //
40  // A more extensive derrivation can be found in the pixman radial gradient
41  // code.
42
43  float2 p = float2(sceneSpaceOutput.x * transform._11 + sceneSpaceOutput.y * transform._21 + transform._31,
44                    sceneSpaceOutput.x * transform._12 + sceneSpaceOutput.y * transform._22 + transform._32);
45  float3 dp = float3(p - center1, radius1);
46
47  // dpx * dcx + dpy * dcy + r * dr
48  float B = dot(dp, diff);
49
50  float C = pow(dp.x, 2) + pow(dp.y, 2) - sq_radius1;
51
52  float det = pow(B, 2) - A * C;
53
54  float sqrt_det = sqrt(abs(det));
55
56  float2 t = (B + float2(sqrt_det, -sqrt_det)) / A;
57
58  float2 isValid = step(float2(-radius1, -radius1), t * diff.z);
59
60  float upper_t = lerp(t.y, t.x, isValid.x);
61
62  // Addressing mode bug work-around.. first let's see if we should consider odd repetitions separately.
63  float oddeven = abs(fmod(floor(upper_t), 2)) * allow_odd;
64
65  // Now let's calculate even or odd addressing in a branchless manner.
66  float upper_t_repeated = ((upper_t - floor(upper_t)) * (1.0f - oddeven)) + ((ceil(upper_t) - upper_t) * oddeven);
67
68  float4 output = GradientTexture.Sample(GradientSampler, float2(upper_t * (1.0f - repeat_correct) + upper_t_repeated * repeat_correct, 0.5));
69  // Premultiply
70  output.rgb *= output.a;
71  // Multiply the output color by the input mask for the operation.
72  output *= InputTexture.Sample(InputSampler, texelSpaceInput0.xy);
73
74  // In order to compile for PS_4_0_level_9_3 we need to be branchless.
75  // This is essentially returning nothing, i.e. bailing early if:
76  // det < 0 || max(isValid.x, isValid.y) <= 0
77  return output * abs(step(max(isValid.x, isValid.y), 0) - 1.0f) * step(0, det);
78};
79
80float4 SampleRadialGradientA0PS(
81    float4 clipSpaceOutput  : SV_POSITION,
82    float4 sceneSpaceOutput : SCENE_POSITION,
83    float4 texelSpaceInput0 : TEXCOORD0
84    ) : SV_Target
85{
86  // This simpler shader is used for the degenerate case where A is 0,
87  // i.e. we're actually solving a linear equation.
88
89  float2 p = float2(sceneSpaceOutput.x * transform._11 + sceneSpaceOutput.y * transform._21 + transform._31,
90                    sceneSpaceOutput.x * transform._12 + sceneSpaceOutput.y * transform._22 + transform._32);
91  float3 dp = float3(p - center1, radius1);
92
93  // dpx * dcx + dpy * dcy + r * dr
94  float B = dot(dp, diff);
95
96  float C = pow(dp.x, 2) + pow(dp.y, 2) - pow(radius1, 2);
97
98  float t = 0.5 * C / B;
99
100  // Addressing mode bug work-around.. first let's see if we should consider odd repetitions separately.
101  float oddeven = abs(fmod(floor(t), 2)) * allow_odd;
102
103  // Now let's calculate even or odd addressing in a branchless manner.
104  float t_repeated = ((t - floor(t)) * (1.0f - oddeven)) + ((ceil(t) - t) * oddeven);
105
106  float4 output = GradientTexture.Sample(GradientSampler, float2(t * (1.0f - repeat_correct) + t_repeated * repeat_correct, 0.5));
107  // Premultiply
108  output.rgb *= output.a;
109  // Multiply the output color by the input mask for the operation.
110  output *= InputTexture.Sample(InputSampler, texelSpaceInput0.xy);
111
112  // In order to compile for PS_4_0_level_9_3 we need to be branchless.
113  // This is essentially returning nothing, i.e. bailing early if:
114  // -radius1 >= t * diff.z
115  return output * abs(step(t * diff.z, -radius1) - 1.0f);
116};
117
118