1 #ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__
2 #define __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__
5 * Copyright (c) 2015 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/image-actor.h>
23 #include <dali/public-api/shader-effects/shader-effect.h>
32 * @brief Set the properties for the motion blur
34 * @param numBlurSamples Number of samples used by the shader
36 inline void SetMotionBlurProperties( Actor& actor, unsigned int numBlurSamples = 8 )
38 actor.RegisterProperty( "uBlurTexCoordScale", 0.125f );
39 actor.RegisterProperty( "uGeometryStretchFactor", 0.05f );
40 actor.RegisterProperty( "uSpeedScalingFactor", 0.5f );
41 actor.RegisterProperty( "uObjectFadeStart", Vector2( 0.25f, 0.25f ) );
42 actor.RegisterProperty( "uObjectFadeEnd", Vector2( 0.5f, 0.5f ) );
43 actor.RegisterProperty( "uAlphaScale", 0.75f );
44 actor.RegisterProperty( "uNumSamples", static_cast<float>( numBlurSamples ) );
45 actor.RegisterProperty( "uRecipNumSamples", 1.0f / static_cast<float>( numBlurSamples ) );
46 actor.RegisterProperty( "uRecipNumSamplesMinusOne", 1.0f / static_cast<float>( numBlurSamples - 1.0f ) );
47 Property::Index uModelProperty = actor.RegisterProperty( "uModelLastFrame", Matrix::IDENTITY );
49 Constraint constraint = Constraint::New<Matrix>( actor, uModelProperty, EqualToConstraint() );
50 constraint.AddSource( Source( actor , Actor::Property::WORLD_MATRIX ) );
55 * @brief Create a new MotionBlurEffect
57 * Motion blur shader works on a per object basis. Objects will
58 * blur when they move, or if the camera moves.
60 * Animatable/Constrainable uniforms:
61 * "uBlurTexCoordScale" - This scales the offset for texture samples along the motion velocity vector.
62 * A smaller value means the samples will be spaced closer, larger value further
63 * apart. User should use this to get the blur to look contiguous, i.e. the blur
64 * texels should not be too widely spread, with gaps in between. Default 0.125.
65 * "uGeometryStretchFactor" - This scales the amount the geometry stretches backwards along the motion velocity
66 * vector. A smaller value means the geometry stretches less, larger it stretches more.
67 * User should use this to get the blur to 'bleed' into areas outside the physical
68 * bounds of the actor. We need this as the blur is only applied inside the bounds of
69 * the actor, but you would expect motion blur trails where the actor was previously
70 * but is there no longer. Default 0.05.
71 * "uSpeedScalingFactor" - This takes the magnitude of the motion velocity vector and scales it to produce a
72 * value which is used to fade the blur in / out with the speed that the actor is moving.
73 * As the blur fades in, more of the blur is visible and less of the original actor, and
74 * viceversa. This value is also used to control how much to fade the actor near the
75 * edges, based on the speed the actor is moving. When the actor is at rest this is not applied.
77 * "uObjectFadeStart" - The displacement from the centre of the actor that the actor will start to fade towards its
78 * edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
79 * Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
80 * not applied. Default 0.25, which is half way towards the edge for an ImageRenderer::QUAD.
81 * "uObjectFadeEnd" - The displacement from the centre of the actor that the actor will finish fading 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 0.5, which is all the way towards the edge for an ImageRenderer::QUAD.
85 * "uAlphaScale" - Global scaler applied to the alpha of the actor. Used to make the blurred actor a bit more subtle
86 * (helps to hide discontinuities due to limited number of texture samples) and reveal a bit of the
87 * background behind it as it moves. When the actor is at rest this is not applied. Default 0.75.
88 * "uNumSamples" - The number of texture samples to be taken. Increasing the number of samples provides better quality
89 * at the cost of performance.
90 * "uModelLastFrame" - The model to world space transformation matrix of the actor in the previous frame.
92 * @return The newly created Property::Map with the motion blur effect
94 inline Property::Map CreateMotionBlurEffect()
96 std::string vertexSource;
98 "precision mediump float;\n"
100 "attribute vec2 aPosition;\n"
102 "uniform mat4 uMvpMatrix;\n"
103 "uniform mat4 uModelView;\n"
104 "uniform mat4 uViewMatrix;\n"
105 "uniform mat4 uProjection;\n"
106 "uniform vec3 uSize;\n"
108 "uniform mat4 uModelLastFrame;\n"
109 "float timeDelta = 0.0167;\n"
111 "uniform float uGeometryStretchFactor;\n"
112 "uniform float uSpeedScalingFactor;\n"
115 "varying vec2 vModelSpaceCenterToPos;\n"
116 "varying vec2 vScreenSpaceVelocityVector;\n"
117 "varying float vSpeed;\n"
118 "varying vec2 vTexCoord;\n"
122 // get view space position of vertex this frame and last frame
123 " vec4 vertexPosition = vec4(aPosition, 0.0, 1.0);\n"
124 " vertexPosition.xyz *= uSize;\n"
126 " vec4 viewSpaceVertex = uModelView * vertexPosition;\n"
127 " vec4 viewSpaceVertexLastFrame = (uViewMatrix * uModelLastFrame) * vertexPosition;\n"
128 " float reciprocalTimeDelta = 1.0 / timeDelta;\n"
130 // work out vertex's last movement in view space
131 " vec3 viewSpacePosDelta = viewSpaceVertex.xyz - viewSpaceVertexLastFrame.xyz;\n"
133 // get clip space position of vertex this frame and last frame
134 " vec4 clipSpaceVertex = uMvpMatrix * vertexPosition;\n"
135 " vec4 clipSpaceVertexLastFrame = uProjection * viewSpaceVertexLastFrame;\n"
137 // decide how much this vertex is 'trailing', i.e. at the back of the object relative to its direction of motion. We do this
138 // 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
140 " float posDeltaLength = length(viewSpacePosDelta);\n"
141 " if(posDeltaLength > 0.001)\n" // avoid div by 0 if object has barely moved
143 " vec4 viewSpaceCenterToPos = uModelView * vec4(vertexPosition.xy, 0.0, 0.0);\n"
144 " float centerToVertexDist = length(viewSpaceCenterToPos);\n"
145 " if(centerToVertexDist > 0.001)\n" // avoid div by 0 if object has vertex at model space origin
147 " vec3 viewSpacePosDeltaNormalised = viewSpacePosDelta / posDeltaLength;\n"
148 " vec3 viewSpaceCenterToPosNormalised = viewSpaceCenterToPos.xyz / centerToVertexDist;\n"
149 " t = (dot(viewSpacePosDeltaNormalised, viewSpaceCenterToPosNormalised) * 0.5 ) + 0.5;\n" // scale and bias from [-1..1] to [0..1]
152 // output vertex position lerped with its last position, based on how much it is trailing,
153 // this stretches the geom back along where it has just been, giving a warping effect
154 // 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)
155 " gl_Position = mix(clipSpaceVertexLastFrame, clipSpaceVertex, t * uGeometryStretchFactor * reciprocalTimeDelta);\n"
157 // work out vertex's last movement in normalised device coordinates [-1..1] space, i.e. perspective divide
158 " vec2 ndcVertex = clipSpaceVertex.xy / clipSpaceVertex.w;\n"
159 " vec2 ndcVertexLastFrame = clipSpaceVertexLastFrame.xy / clipSpaceVertexLastFrame.w;\n"
160 // scale and bias so that a value of 1.0 corresponds to screen size (NDC is [-1..1] = 2)
161 " vScreenSpaceVelocityVector = ((ndcVertex - ndcVertexLastFrame) * 0.5 * reciprocalTimeDelta);\n"
162 " vScreenSpaceVelocityVector.y = -vScreenSpaceVelocityVector.y;\n" // TODO negated due to y being inverted in our coordinate system?
163 // calculate a scaling factor proportional to velocity, which we can use to tweak how things look
164 " vSpeed = length(vScreenSpaceVelocityVector) * uSpeedScalingFactor;\n"
165 " vSpeed = clamp(vSpeed, 0.0, 1.0);\n"
167 // 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)
168 " vModelSpaceCenterToPos = viewSpaceVertex.xy;\n"
170 " vec2 texCoord = aPosition + vec2(0.5);"
171 " vTexCoord = texCoord;\n"
175 std::string fragmentSource;
177 "precision mediump float;\n"
179 "uniform sampler2D sTexture;\n"
180 "uniform vec4 uColor;\n"
182 "uniform vec2 uObjectFadeStart;\n"
183 "uniform vec2 uObjectFadeEnd;\n"
184 "uniform float uAlphaScale;\n"
185 "uniform float uBlurTexCoordScale;\n"
186 "uniform float uNumSamples;\n"
187 "uniform float uRecipNumSamples;\n"
188 "uniform float uRecipNumSamplesMinusOne;\n"
190 "varying vec2 vModelSpaceCenterToPos;\n"
191 "varying vec2 vScreenSpaceVelocityVector;\n"
192 "varying float vSpeed;\n"
193 "varying vec2 vTexCoord;\n"
197 // 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
198 // the blurred object and the unblurred background. Use smoothstep also to hide any hard edges (discontinuities) in rate of change of this alpha gradient
199 " vec2 centerToPixel = abs(vModelSpaceCenterToPos);\n"
200 " vec2 fadeToEdges = smoothstep(0.0, 1.0, 1.0 - ((centerToPixel - uObjectFadeStart) / (uObjectFadeEnd - uObjectFadeStart)));\n"
201 " float fadeToEdgesScale = fadeToEdges.x * fadeToEdges.y * uAlphaScale;\n" // apply global scaler
202 " fadeToEdgesScale = mix(1.0, fadeToEdgesScale, vSpeed);\n" // fade proportional to speed, so opaque when at rest
204 // scale velocity vector by user requirements
205 " vec2 velocity = vScreenSpaceVelocityVector * uBlurTexCoordScale;\n"
207 // standard actor texel
208 " vec4 colActor = texture2D(sTexture, vTexCoord);\n"
210 // blurred actor - gather texture samples from the actor texture in the direction of motion
211 " vec4 col = colActor * uRecipNumSamples;\n"
212 " for(float i = 1.0; i < uNumSamples; i += 1.0)\n"
214 " float t = i * uRecipNumSamplesMinusOne;\n"
215 " col += texture2D(sTexture, vTexCoord + (velocity * t)) * uRecipNumSamples;\n"
217 " gl_FragColor = mix(colActor, col, vSpeed);\n" // lerp blurred and non-blurred actor based on speed of motion
218 " gl_FragColor.a = fadeToEdgesScale;//colActor.a * fadeToEdgesScale;\n" // fade blurred actor to its edges based on speed of motion
219 " gl_FragColor *= uColor;\n"
225 Property::Map customShader;
226 customShader[ "vertexShader" ] = vertexSource;
227 customShader[ "fragmentShader" ] = fragmentSource;
229 customShader[ "subdivideGridX" ] = 10;
230 customShader[ "subdivideGridY" ] = 10;
232 // NOTE: we must turn on alpha blending for the actor (HINT_BLENDING)
233 customShader[ "hints" ] = "outputIsTransparent";
235 map[ "shader" ] = customShader;
243 #endif //#ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__