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 Create a new MotionBlurEffect
34 * Motion blur shader works on a per object basis. Objects will
35 * blur when they move, or if the camera moves. Can be applied to ImageActor or
40 * // Create shader used for doing motion blur\n
41 * ShaderEffect MotionBlurEffect = CreateMotionBlurEffect();
43 * // set actor shader to the blur one\n
44 * Actor actor = Actor::New( ... );\n
45 * actor.SetShaderEffect( MotionBlurEffect );
47 * // Constrain "uModelLastFrame" to be the same as the actor's world matrix\n
48 * Dali::Property::Index uModelProperty = MotionBlurEffect.GetPropertyIndex( "uModelLastFrame" );
49 * Constraint constraint = Constraint::New<Matrix>( MotionBlurEffect, uModelProperty, EqualToConstraint() );\n
50 * constraint.AddSource( Source( actor , Actor::Property::WORLD_MATRIX ) );\n
51 * constraint.Apply();\n
54 * Animatable/Constrainable uniforms:
55 * "uBlurTexCoordScale" - This scales the offset for texture samples along the motion velocity vector.
56 * A smaller value means the samples will be spaced closer, larger value further
57 * apart. User should use this to get the blur to look contiguous, i.e. the blur
58 * texels should not be too widely spread, with gaps in between. Default 0.125.
59 * "uGeometryStretchFactor" - This scales the amount the geometry stretches backwards along the motion velocity
60 * vector. A smaller value means the geometry stretches less, larger it stretches more.
61 * User should use this to get the blur to 'bleed' into areas outside the physical
62 * bounds of the actor. We need this as the blur is only applied inside the bounds of
63 * the actor, but you would expect motion blur trails where the actor was previously
64 * but is there no longer. Default 0.05.
65 * "uSpeedScalingFactor" - This takes the magnitude of the motion velocity vector and scales it to produce a
66 * value which is used to fade the blur in / out with the speed that the actor is moving.
67 * As the blur fades in, more of the blur is visible and less of the original actor, and
68 * viceversa. This value is also used to control how much to fade the actor near the
69 * edges, based on the speed the actor is moving. When the actor is at rest this is not applied.
71 * "uObjectFadeStart" - The displacement from the centre of the actor that the actor will start to fade towards its
72 * edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
73 * Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
74 * not applied. Default 0.25, which is half way towards the edge for an ImageRenderer::QUAD.
75 * "uObjectFadeEnd" - The displacement from the centre of the actor that the actor will finish fading towards its
76 * edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
77 * Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
78 * not applied.Default 0.5, which is all the way towards the edge for an ImageRenderer::QUAD.
79 * "uAlphaScale" - Global scaler applied to the alpha of the actor. Used to make the blurred actor a bit more subtle
80 * (helps to hide discontinuities due to limited number of texture samples) and reveal a bit of the
81 * background behind it as it moves. When the actor is at rest this is not applied. Default 0.75.
82 * "uNumSamples" - The number of texture samples to be taken. Increasing the number of samples provides better quality
83 * at the cost of performance.
84 * "uModelLastFrame" - The model to world space transformation matrix of the actor in the previous frame.
86 * @param numBlurSamples Number of samples used by the shader
87 * @return A handle to a newly allocated ShaderEffect
89 inline ShaderEffect CreateMotionBlurEffect( unsigned int numBlurSamples = 8 )
91 // Dali vertexSource prefix for reference:
92 // precision highp float;
93 // attribute vec3 aPosition;
94 // attribute vec2 aTexCoord;
95 // uniform mat4 uMvpMatrix;
96 // uniform mat4 uModelView;
97 // uniform mat3 uNormalMatrix;
98 // uniform mat4 uProjection;
99 // uniform vec4 uColor;
100 // varying vec2 vTexCoord;
101 std::string vertexSource;
103 "precision mediump float;\n"
104 "uniform mat4 uModelLastFrame;\n"
105 "uniform float uTimeDelta;\n"
107 "uniform float uGeometryStretchFactor;\n"
108 "uniform float uSpeedScalingFactor;\n"
111 "varying vec2 vModelSpaceCenterToPos;\n"
112 "varying vec2 vScreenSpaceVelocityVector;\n"
113 "varying float vSpeed;\n"
117 // get view space position of vertex this frame and last frame
118 " vec4 vertex = vec4(aPosition, 1.0);\n"
119 " vec4 viewSpaceVertex = uModelView * vertex;\n"
120 " vec4 viewSpaceVertexLastFrame = (uViewMatrix * uModelLastFrame) * vertex;\n"
121 " float reciprocalTimeDelta = 1.0 / ((uTimeDelta > 0.0) ? uTimeDelta : 0.01);\n"
123 // work out vertex's last movement in view space
124 " vec3 viewSpacePosDelta = viewSpaceVertex.xyz - viewSpaceVertexLastFrame.xyz;\n"
126 // get clip space position of vertex this frame and last frame
127 " vec4 clipSpaceVertex = uMvpMatrix * vertex;\n"
128 " vec4 clipSpaceVertexLastFrame = uProjection * viewSpaceVertexLastFrame;\n"
130 // decide how much this vertex is 'trailing', i.e. at the back of the object relative to its direction of motion. We do this
131 // 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
133 " float posDeltaLength = length(viewSpacePosDelta);\n"
134 " if(posDeltaLength > 0.001)\n" // avoid div by 0 if object has barely moved
136 " vec4 viewSpaceCenterToPos = uModelView * vec4(aPosition, 0.0);\n"
137 " float centerToVertexDist = length(viewSpaceCenterToPos);\n"
138 " if(centerToVertexDist > 0.001)\n" // avoid div by 0 if object has vertex at model space origin
140 " vec3 viewSpacePosDeltaNormalised = viewSpacePosDelta / posDeltaLength;\n"
141 " vec3 viewSpaceCenterToPosNormalised = viewSpaceCenterToPos.xyz / centerToVertexDist;\n"
142 " t = (dot(viewSpacePosDeltaNormalised, viewSpaceCenterToPosNormalised) * 0.5 ) + 0.5;\n" // scale and bias from [-1..1] to [0..1]
145 // output vertex position lerped with its last position, based on how much it is trailing,
146 // this stretches the geom back along where it has just been, giving a warping effect
147 // 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)
148 " gl_Position = mix(clipSpaceVertexLastFrame, clipSpaceVertex, t * uGeometryStretchFactor * reciprocalTimeDelta);\n"
150 // work out vertex's last movement in normalised device coordinates [-1..1] space, i.e. perspective divide
151 " vec2 ndcVertex = clipSpaceVertex.xy / clipSpaceVertex.w;\n"
152 " vec2 ndcVertexLastFrame = clipSpaceVertexLastFrame.xy / clipSpaceVertexLastFrame.w;\n"
153 // scale and bias so that a value of 1.0 corresponds to screen size (NDC is [-1..1] = 2)
154 " vScreenSpaceVelocityVector = ((ndcVertex - ndcVertexLastFrame) * 0.5 * reciprocalTimeDelta);\n"
155 " vScreenSpaceVelocityVector.y = -vScreenSpaceVelocityVector.y;\n" // TODO negated due to y being inverted in our coordinate system?
156 // calculate a scaling factor proportional to velocity, which we can use to tweak how things look
157 " vSpeed = length(vScreenSpaceVelocityVector) * uSpeedScalingFactor;\n"
158 " vSpeed = clamp(vSpeed, 0.0, 1.0);\n"
160 // 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)
161 " vModelSpaceCenterToPos = aPosition.xy;\n"
163 " vTexCoord = aTexCoord;\n"
167 // Dali fragmentSource prefix for reference:
168 // precision highp float;
169 // uniform sampler2D sTexture;
170 // uniform sampler2D sEffect;
171 // uniform vec4 uColor;
172 // varying vec2 vTexCoord;
173 std::string fragmentSource;
175 "precision mediump float;\n"
176 "uniform vec2 uObjectFadeStart;\n"
177 "uniform vec2 uObjectFadeEnd;\n"
178 "uniform float uAlphaScale;\n"
179 "uniform float uBlurTexCoordScale;\n"
180 "uniform float uNumSamples;\n"
181 "uniform float uRecipNumSamples;\n"
182 "uniform float uRecipNumSamplesMinusOne;\n"
184 "varying vec2 vModelSpaceCenterToPos;\n"
185 "varying vec2 vScreenSpaceVelocityVector;\n"
186 "varying float vSpeed;\n"
190 // 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
191 // the blurred object and the unblurred background. Use smoothstep also to hide any hard edges (discontinuities) in rate of change of this alpha gradient
192 " vec2 centerToPixel = abs(vModelSpaceCenterToPos);\n"
193 " vec2 fadeToEdges = smoothstep(0.0, 1.0, 1.0 - ((centerToPixel - uObjectFadeStart) / (uObjectFadeEnd - uObjectFadeStart)));\n"
194 " float fadeToEdgesScale = fadeToEdges.x * fadeToEdges.y * uAlphaScale;\n" // apply global scaler
195 " fadeToEdgesScale = mix(1.0, fadeToEdgesScale, vSpeed);\n" // fade proportional to speed, so opaque when at rest
197 // scale velocity vector by user requirements
198 " vec2 velocity = vScreenSpaceVelocityVector * uBlurTexCoordScale;\n"
200 // standard actor texel
201 " vec4 colActor = texture2D(sTexture, vTexCoord);\n"
203 // blurred actor - gather texture samples from the actor texture in the direction of motion
204 " vec4 col = colActor * uRecipNumSamples;\n"
205 " for(float i = 1.0; i < uNumSamples; i += 1.0)\n"
207 " float t = i * uRecipNumSamplesMinusOne;\n"
208 " col += texture2D(sTexture, vTexCoord + (velocity * t)) * uRecipNumSamples;\n"
210 " gl_FragColor = mix(colActor, col, vSpeed);\n" // lerp blurred and non-blurred actor based on speed of motion
211 " gl_FragColor.a = colActor.a * fadeToEdgesScale;\n" // fade blurred actor to its edges based on speed of motion
212 " gl_FragColor *= uColor;\n"
215 // NOTE: we must turn on alpha blending for the actor (HINT_BLENDING)
216 ShaderEffect shader = ShaderEffect::New( vertexSource, fragmentSource,
217 ShaderEffect::GeometryHints( ShaderEffect::HINT_BLENDING | ShaderEffect::HINT_GRID) );
219 //////////////////////////////////////
220 // Register uniform properties
223 shader.SetUniform( "uBlurTexCoordScale", 0.125f );
224 shader.SetUniform( "uGeometryStretchFactor", 0.05f );
225 shader.SetUniform( "uSpeedScalingFactor", 0.5f );
226 shader.SetUniform( "uObjectFadeStart", Vector2( 0.25f, 0.25f ) );
227 shader.SetUniform( "uObjectFadeEnd", Vector2( 0.5f, 0.5f ) );
228 shader.SetUniform( "uAlphaScale", 0.75f );
229 shader.SetUniform( "uNumSamples", static_cast<float>( numBlurSamples ) );
230 shader.SetUniform( "uRecipNumSamples", 1.0f / static_cast<float>( numBlurSamples ) );
231 shader.SetUniform( "uRecipNumSamplesMinusOne", 1.0f / static_cast<float>( numBlurSamples - 1.0f ) );
232 shader.SetUniform( "uModelLastFrame", Matrix::IDENTITY );
241 #endif //#ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__