1 #ifndef DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H
2 #define DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H
5 * Copyright (c) 2020 Samsung Electronics Co., Ltd.
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
22 #include <dali/public-api/actors/actor.h>
23 #include <dali/public-api/animation/constraint.h>
24 #include <dali/public-api/object/property-map.h>
25 #include <dali/public-api/rendering/shader.h>
28 #include <dali-toolkit/public-api/visuals/visual-properties.h>
35 * @brief Set the properties for the motion blur
37 * @param[in] actor The actor that registers the uniform properties
38 * @param[in] numBlurSamples Number of samples used by the shader
40 inline void SetMotionBlurProperties(Actor& actor, unsigned int numBlurSamples = 8)
42 actor.RegisterProperty("uBlurTexCoordScale", 0.125f);
43 actor.RegisterProperty("uGeometryStretchFactor", 0.05f);
44 actor.RegisterProperty("uSpeedScalingFactor", 0.5f);
45 actor.RegisterProperty("uObjectFadeStart", Vector2(0.25f, 0.25f));
46 actor.RegisterProperty("uObjectFadeEnd", Vector2(0.5f, 0.5f));
47 actor.RegisterProperty("uAlphaScale", 0.75f);
48 actor.RegisterProperty("uNumSamples", static_cast<float>(numBlurSamples));
49 actor.RegisterProperty("uRecipNumSamples", 1.0f / static_cast<float>(numBlurSamples));
50 actor.RegisterProperty("uRecipNumSamplesMinusOne", 1.0f / static_cast<float>(numBlurSamples - 1.0f));
51 Property::Index uModelProperty = actor.RegisterProperty("uModelLastFrame", Matrix::IDENTITY);
53 Constraint constraint = Constraint::New<Matrix>(actor, uModelProperty, EqualToConstraint());
54 constraint.AddSource(Source(actor, Actor::Property::WORLD_MATRIX));
59 * @brief Create a new MotionBlurEffect
61 * Motion blur shader works on a per object basis. Objects will
62 * blur when they move, or if the camera moves.
64 * Animatable/Constrainable uniforms:
65 * "uBlurTexCoordScale" - This scales the offset for texture samples along the motion velocity vector.
66 * A smaller value means the samples will be spaced closer, larger value further
67 * apart. User should use this to get the blur to look contiguous, i.e. the blur
68 * texels should not be too widely spread, with gaps in between. Default 0.125.
69 * "uGeometryStretchFactor" - This scales the amount the geometry stretches backwards along the motion velocity
70 * vector. A smaller value means the geometry stretches less, larger it stretches more.
71 * User should use this to get the blur to 'bleed' into areas outside the physical
72 * bounds of the actor. We need this as the blur is only applied inside the bounds of
73 * the actor, but you would expect motion blur trails where the actor was previously
74 * but is there no longer. Default 0.05.
75 * "uSpeedScalingFactor" - This takes the magnitude of the motion velocity vector and scales it to produce a
76 * value which is used to fade the blur in / out with the speed that the actor is moving.
77 * As the blur fades in, more of the blur is visible and less of the original actor, and
78 * viceversa. This value is also used to control how much to fade the actor near the
79 * edges, based on the speed the actor is moving. When the actor is at rest this is not applied.
81 * "uObjectFadeStart" - The displacement from the centre of the actor that the actor will start to fade towards its
82 * edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
83 * Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
84 * not applied. Default 0.25, which is half way towards the edge for an ImageVisual::QUAD.
85 * "uObjectFadeEnd" - The displacement from the centre of the actor that the actor will finish fading towards its
86 * edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
87 * Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
88 * not applied.Default 0.5, which is all the way towards the edge for an ImageVisual::QUAD.
89 * "uAlphaScale" - Global scaler applied to the alpha of the actor. Used to make the blurred actor a bit more subtle
90 * (helps to hide discontinuities due to limited number of texture samples) and reveal a bit of the
91 * background behind it as it moves. When the actor is at rest this is not applied. Default 0.75.
92 * "uNumSamples" - The number of texture samples to be taken. Increasing the number of samples provides better quality
93 * at the cost of performance.
94 * "uModelLastFrame" - The model to world space transformation matrix of the actor in the previous frame.
96 * @return The newly created Property::Map with the motion blur effect
98 inline Property::Map CreateMotionBlurEffect()
100 std::string vertexSource;
102 "precision mediump float;\n"
104 "attribute vec2 aPosition;\n"
106 "uniform mat4 uMvpMatrix;\n"
107 "uniform mat4 uModelView;\n"
108 "uniform mat4 uViewMatrix;\n"
109 "uniform mat4 uProjection;\n"
110 "uniform vec3 uSize;\n"
112 "uniform mat4 uModelLastFrame;\n"
113 "float timeDelta = 0.0167;\n"
115 "uniform float uGeometryStretchFactor;\n"
116 "uniform float uSpeedScalingFactor;\n"
119 "varying vec2 vModelSpaceCenterToPos;\n"
120 "varying vec2 vScreenSpaceVelocityVector;\n"
121 "varying float vSpeed;\n"
122 "varying vec2 vTexCoord;\n"
126 // get view space position of vertex this frame and last frame
127 " vec4 vertexPosition = vec4(aPosition, 0.0, 1.0);\n"
128 " vertexPosition.xyz *= uSize;\n"
130 " vec4 viewSpaceVertex = uModelView * vertexPosition;\n"
131 " vec4 viewSpaceVertexLastFrame = (uViewMatrix * uModelLastFrame) * vertexPosition;\n"
132 " float reciprocalTimeDelta = 1.0 / timeDelta;\n"
134 // work out vertex's last movement in view space
135 " vec3 viewSpacePosDelta = viewSpaceVertex.xyz - viewSpaceVertexLastFrame.xyz;\n"
137 // get clip space position of vertex this frame and last frame
138 " vec4 clipSpaceVertex = uMvpMatrix * vertexPosition;\n"
139 " vec4 clipSpaceVertexLastFrame = uProjection * viewSpaceVertexLastFrame;\n"
141 // decide how much this vertex is 'trailing', i.e. at the back of the object relative to its direction of motion. We do this
142 // by assuming the objects model space origin is at its center and taking the dot product of the vector from center to vertex with the motion direction
144 " float posDeltaLength = length(viewSpacePosDelta);\n"
145 " if(posDeltaLength > 0.001)\n" // avoid div by 0 if object has barely moved
147 " vec4 viewSpaceCenterToPos = uModelView * vec4(vertexPosition.xy, 0.0, 0.0);\n"
148 " float centerToVertexDist = length(viewSpaceCenterToPos);\n"
149 " if(centerToVertexDist > 0.001)\n" // avoid div by 0 if object has vertex at model space origin
151 " vec3 viewSpacePosDeltaNormalised = viewSpacePosDelta / posDeltaLength;\n"
152 " vec3 viewSpaceCenterToPosNormalised = viewSpaceCenterToPos.xyz / centerToVertexDist;\n"
153 " t = (dot(viewSpacePosDeltaNormalised, viewSpaceCenterToPosNormalised) * 0.5 ) + 0.5;\n" // scale and bias from [-1..1] to [0..1]
156 // output vertex position lerped with its last position, based on how much it is trailing,
157 // this stretches the geom back along where it has just been, giving a warping effect
158 // Note: we must take account of time delta to convert position delta into a velocity, so changes are smooth (take into account frame time correctly)
159 " gl_Position = mix(clipSpaceVertexLastFrame, clipSpaceVertex, t * uGeometryStretchFactor * reciprocalTimeDelta);\n"
161 // work out vertex's last movement in normalised device coordinates [-1..1] space, i.e. perspective divide
162 " vec2 ndcVertex = clipSpaceVertex.xy / clipSpaceVertex.w;\n"
163 " vec2 ndcVertexLastFrame = clipSpaceVertexLastFrame.xy / clipSpaceVertexLastFrame.w;\n"
164 // scale and bias so that a value of 1.0 corresponds to screen size (NDC is [-1..1] = 2)
165 " vScreenSpaceVelocityVector = ((ndcVertex - ndcVertexLastFrame) * 0.5 * reciprocalTimeDelta);\n"
166 " vScreenSpaceVelocityVector.y = -vScreenSpaceVelocityVector.y;\n" // TODO negated due to y being inverted in our coordinate system?
167 // calculate a scaling factor proportional to velocity, which we can use to tweak how things look
168 " vSpeed = length(vScreenSpaceVelocityVector) * uSpeedScalingFactor;\n"
169 " vSpeed = clamp(vSpeed, 0.0, 1.0);\n"
171 // provide fragment shader with vector from center of object to pixel (assumes the objects model space origin is at its center and verts have same z)
172 " vModelSpaceCenterToPos = viewSpaceVertex.xy;\n"
174 " vec2 texCoord = aPosition + vec2(0.5);"
175 " vTexCoord = texCoord;\n"
178 std::string fragmentSource;
180 "precision mediump float;\n"
182 "uniform sampler2D sTexture;\n"
183 "uniform vec4 uColor;\n"
185 "uniform vec2 uObjectFadeStart;\n"
186 "uniform vec2 uObjectFadeEnd;\n"
187 "uniform float uAlphaScale;\n"
188 "uniform float uBlurTexCoordScale;\n"
189 "uniform float uNumSamples;\n"
190 "uniform float uRecipNumSamples;\n"
191 "uniform float uRecipNumSamplesMinusOne;\n"
193 "varying vec2 vModelSpaceCenterToPos;\n"
194 "varying vec2 vScreenSpaceVelocityVector;\n"
195 "varying float vSpeed;\n"
196 "varying vec2 vTexCoord;\n"
200 // calculate an alpha value that will fade the object towards its extremities, we need this to avoid an unsightly hard edge between color values of
201 // the blurred object and the unblurred background. Use smoothstep also to hide any hard edges (discontinuities) in rate of change of this alpha gradient
202 " vec2 centerToPixel = abs(vModelSpaceCenterToPos);\n"
203 " vec2 fadeToEdges = smoothstep(0.0, 1.0, 1.0 - ((centerToPixel - uObjectFadeStart) / (uObjectFadeEnd - uObjectFadeStart)));\n"
204 " float fadeToEdgesScale = fadeToEdges.x * fadeToEdges.y * uAlphaScale;\n" // apply global scaler
205 " fadeToEdgesScale = mix(1.0, fadeToEdgesScale, vSpeed);\n" // fade proportional to speed, so opaque when at rest
207 // scale velocity vector by user requirements
208 " vec2 velocity = vScreenSpaceVelocityVector * uBlurTexCoordScale;\n"
210 // standard actor texel
211 " vec4 colActor = texture2D(sTexture, vTexCoord);\n"
213 // blurred actor - gather texture samples from the actor texture in the direction of motion
214 " vec4 col = colActor * uRecipNumSamples;\n"
215 " for(float i = 1.0; i < uNumSamples; i += 1.0)\n"
217 " float t = i * uRecipNumSamplesMinusOne;\n"
218 " col += texture2D(sTexture, vTexCoord + (velocity * t)) * uRecipNumSamples;\n"
220 " gl_FragColor = mix(colActor, col, vSpeed);\n" // lerp blurred and non-blurred actor based on speed of motion
221 " gl_FragColor.a = fadeToEdgesScale;//colActor.a * fadeToEdgesScale;\n" // fade blurred actor to its edges based on speed of motion
222 " gl_FragColor *= uColor;\n"
227 Property::Map customShader;
228 customShader[Visual::Shader::Property::VERTEX_SHADER] = vertexSource;
229 customShader[Visual::Shader::Property::FRAGMENT_SHADER] = fragmentSource;
231 customShader[Visual::Shader::Property::SUBDIVIDE_GRID_X] = 10;
232 customShader[Visual::Shader::Property::SUBDIVIDE_GRID_Y] = 10;
234 customShader[Visual::Shader::Property::HINTS] = Shader::Hint::OUTPUT_IS_TRANSPARENT;
236 map[Toolkit::Visual::Property::SHADER] = customShader;
240 } // namespace Toolkit
244 #endif // DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H