[platform/core/uifw/dali-toolkit.git] / dali-toolkit / devel-api / shader-effects / motion-blur-effect.h

#ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__
#define __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__

/*
 * Copyright (c) 2015 Samsung Electronics Co., Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

// EXTERNAL INCLUDES
#include <dali/public-api/actors/image-actor.h>
#include <dali/public-api/shader-effects/shader-effect.h>

namespace Dali
{

namespace Toolkit
{

/**
 * @brief Create a new MotionBlurEffect
 *
 * Motion blur shader works on a per object basis. Objects will
 * blur when they move, or if the camera moves. Can be applied to ImageActor or
 * TextActor only.
 *
 * Usage example:-
 *
 * // Create shader used for doing motion blur\n
 * ShaderEffect MotionBlurEffect = CreateMotionBlurEffect();
 *
 * // set actor shader to the blur one\n
 * Actor actor = Actor::New( ... );\n
 * actor.SetShaderEffect( MotionBlurEffect );
 *
 * // Constrain "uModelLastFrame" to be the same as the actor's world matrix\n
 * Dali::Property::Index uModelProperty = MotionBlurEffect.GetPropertyIndex( "uModelLastFrame" );
 * Constraint constraint = Constraint::New<Matrix>( MotionBlurEffect, uModelProperty, EqualToConstraint() );\n
 * constraint.AddSource( Source( actor , Actor::Property::WORLD_MATRIX ) );\n
 * constraint.Apply();\n
 *
 *
 * Animatable/Constrainable uniforms:
 *  "uBlurTexCoordScale"      - This scales the offset for texture samples along the motion velocity vector.
 *                              A smaller value means the samples will be spaced closer, larger value further
 *                              apart. User should use this to get the blur to look contiguous, i.e. the blur
 *                              texels should not be too widely spread, with gaps in between. Default 0.125.
 *  "uGeometryStretchFactor"  - This scales the amount the geometry stretches backwards along the motion velocity
 *                              vector. A smaller value means the geometry stretches less, larger it stretches more.
 *                              User should use this to get the blur to 'bleed' into areas outside the physical
 *                              bounds of the actor. We need this as the blur is only applied inside the bounds of
 *                              the actor, but you would expect motion blur trails where the actor was previously
 *                              but is there no longer. Default 0.05.
 *  "uSpeedScalingFactor"     - This takes the magnitude of the motion velocity vector and scales it to produce a
 *                              value which is used to fade the blur in / out with the speed that the actor is moving.
 *                              As the blur fades in, more of the blur is visible and less of the original actor, and
 *                              viceversa. This value is also used to control how much to fade the actor near the
 *                              edges, based on the speed the actor is moving. When the actor is at rest this is not applied.
 *                              Default 0.5.
 *  "uObjectFadeStart"        - The displacement from the centre of the actor that the actor will start to fade towards its
 *                              edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
 *                              Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
 *                              not applied. Default 0.25, which is half way towards the edge for an ImageRenderer::QUAD.
 *  "uObjectFadeEnd"          - The displacement from the centre of the actor that the actor will finish fading towards its
 *                              edges. This is used to prevent an unsightly hard edge between the blurred actor and the scene.
 *                              Depends on the values of the vertices in the vertex stream. When the actor is at rest this is
 *                              not applied.Default 0.5, which is all the way towards the edge for an ImageRenderer::QUAD.
 *  "uAlphaScale"             - Global scaler applied to the alpha of the actor. Used to make the blurred actor a bit more subtle
 *                              (helps to hide discontinuities due to limited number of texture samples) and reveal a bit of the
 *                              background behind it as it moves. When the actor is at rest this is not applied. Default 0.75.
 *  "uNumSamples"             - The number of texture samples to be taken. Increasing the number of samples provides better quality
 *                              at the cost of performance.
 *  "uModelLastFrame"         - The model to world space transformation matrix of the actor in the previous frame.
 *
 * @param numBlurSamples Number of samples used by the shader
 * @return A handle to a newly allocated ShaderEffect
 */
inline ShaderEffect CreateMotionBlurEffect( unsigned int numBlurSamples = 8 )
{
  // Dali vertexSource prefix for reference:
  // precision highp float;
  // attribute vec3  aPosition;
  // attribute vec2  aTexCoord;
  // uniform   mat4  uMvpMatrix;
  // uniform   mat4  uModelView;
  // uniform   mat3  uNormalMatrix;
  // uniform   mat4  uProjection;
  // uniform   vec4  uColor;
  // varying   vec2  vTexCoord;
  std::string vertexSource;
  vertexSource =
      "precision mediump float;\n"
      "uniform mat4 uModelLastFrame;\n"
      "float timeDelta = 0.0167;\n"

      "uniform float uGeometryStretchFactor;\n"
      "uniform float uSpeedScalingFactor;\n"

      // outputs
      "varying vec2 vModelSpaceCenterToPos;\n"
      "varying vec2 vScreenSpaceVelocityVector;\n"
      "varying float vSpeed;\n"

      "void main()\n"
      "{\n"
      // get view space position of vertex this frame and last frame
      " vec4 vertex = vec4(aPosition, 1.0);\n"
      " vec4 viewSpaceVertex = uModelView * vertex;\n"
      " vec4 viewSpaceVertexLastFrame = (uViewMatrix * uModelLastFrame) * vertex;\n"
      " float reciprocalTimeDelta = 1.0 / timeDelta;\n"

      // work out vertex's last movement in view space
      " vec3 viewSpacePosDelta = viewSpaceVertex.xyz - viewSpaceVertexLastFrame.xyz;\n"

      // get clip space position of vertex this frame and last frame
      " vec4 clipSpaceVertex = uMvpMatrix * vertex;\n"
      " vec4 clipSpaceVertexLastFrame = uProjection * viewSpaceVertexLastFrame;\n"

      // decide how much this vertex is 'trailing', i.e. at the back of the object relative to its direction of motion. We do this
      // 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
      " float t = 0.0;\n"
      " float posDeltaLength = length(viewSpacePosDelta);\n"
      " if(posDeltaLength > 0.001)\n" // avoid div by 0 if object has barely moved
      " {\n"
      "   vec4 viewSpaceCenterToPos = uModelView * vec4(aPosition, 0.0);\n"
      "   float centerToVertexDist = length(viewSpaceCenterToPos);\n"
      "   if(centerToVertexDist > 0.001)\n" // avoid div by 0 if object has vertex at model space origin
      "   {\n"
      "     vec3 viewSpacePosDeltaNormalised = viewSpacePosDelta / posDeltaLength;\n"
      "     vec3 viewSpaceCenterToPosNormalised = viewSpaceCenterToPos.xyz / centerToVertexDist;\n"
      "     t = (dot(viewSpacePosDeltaNormalised, viewSpaceCenterToPosNormalised) * 0.5 ) + 0.5;\n" // scale and bias from [-1..1] to [0..1]
      "   }\n"
      " }\n"
      // output vertex position lerped with its last position, based on how much it is trailing,
      // this stretches the geom back along where it has just been, giving a warping effect
      // 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)
      " gl_Position = mix(clipSpaceVertexLastFrame, clipSpaceVertex, t * uGeometryStretchFactor * reciprocalTimeDelta);\n"

      // work out vertex's last movement in normalised device coordinates [-1..1] space, i.e. perspective divide
      " vec2 ndcVertex = clipSpaceVertex.xy / clipSpaceVertex.w;\n"
      " vec2 ndcVertexLastFrame = clipSpaceVertexLastFrame.xy / clipSpaceVertexLastFrame.w;\n"
      // scale and bias so that a value of 1.0 corresponds to screen size (NDC is [-1..1] = 2)
      " vScreenSpaceVelocityVector = ((ndcVertex - ndcVertexLastFrame) * 0.5 * reciprocalTimeDelta);\n"
      " vScreenSpaceVelocityVector.y = -vScreenSpaceVelocityVector.y;\n" // TODO negated due to y being inverted in our coordinate system?
      // calculate a scaling factor proportional to velocity, which we can use to tweak how things look
      " vSpeed = length(vScreenSpaceVelocityVector) * uSpeedScalingFactor;\n"
      " vSpeed = clamp(vSpeed, 0.0, 1.0);\n"

      // 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)
      " vModelSpaceCenterToPos = aPosition.xy;\n"

      " vTexCoord = aTexCoord;\n"
      "}\n";


  // Dali fragmentSource prefix for reference:
  // precision highp     float;
  // uniform   sampler2D sTexture;
  // uniform   sampler2D sEffect;
  // uniform   vec4      uColor;
  // varying   vec2      vTexCoord;
  std::string fragmentSource;
  fragmentSource =
      "precision mediump float;\n"
      "uniform vec2 uObjectFadeStart;\n"
      "uniform vec2 uObjectFadeEnd;\n"
      "uniform float uAlphaScale;\n"
      "uniform float uBlurTexCoordScale;\n"
      "uniform float uNumSamples;\n"
      "uniform float uRecipNumSamples;\n"
      "uniform float uRecipNumSamplesMinusOne;\n"
      // inputs
      "varying vec2 vModelSpaceCenterToPos;\n"
      "varying vec2 vScreenSpaceVelocityVector;\n"
      "varying float vSpeed;\n"

      "void main()\n"
      "{\n"
      // 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
      // the blurred object and the unblurred background. Use smoothstep also to hide any hard edges (discontinuities) in rate of change of this alpha gradient
      " vec2 centerToPixel = abs(vModelSpaceCenterToPos);\n"
      " vec2 fadeToEdges = smoothstep(0.0, 1.0, 1.0 - ((centerToPixel - uObjectFadeStart) / (uObjectFadeEnd - uObjectFadeStart)));\n"
      " float fadeToEdgesScale = fadeToEdges.x * fadeToEdges.y * uAlphaScale;\n" // apply global scaler
      " fadeToEdgesScale = mix(1.0, fadeToEdgesScale, vSpeed);\n" // fade proportional to speed, so opaque when at rest

      // scale velocity vector by user requirements
      " vec2 velocity = vScreenSpaceVelocityVector * uBlurTexCoordScale;\n"

      // standard actor texel
      " vec4 colActor = texture2D(sTexture, vTexCoord);\n"

      // blurred actor - gather texture samples from the actor texture in the direction of motion
      " vec4 col = colActor * uRecipNumSamples;\n"
      " for(float i = 1.0; i < uNumSamples; i += 1.0)\n"
      " {\n"
      "   float t = i * uRecipNumSamplesMinusOne;\n"
      "   col += texture2D(sTexture, vTexCoord + (velocity * t)) * uRecipNumSamples;\n"
      " }\n"
      " gl_FragColor = mix(colActor, col, vSpeed);\n" // lerp blurred and non-blurred actor based on speed of motion
      " gl_FragColor.a = colActor.a * fadeToEdgesScale;\n" // fade blurred actor to its edges based on speed of motion
      " gl_FragColor *= uColor;\n"
      "}\n";

  // NOTE: we must turn on alpha blending for the actor (HINT_BLENDING)
  ShaderEffect shader = ShaderEffect::New( vertexSource, fragmentSource,
                                           ShaderEffect::GeometryHints( ShaderEffect::HINT_BLENDING | ShaderEffect::HINT_GRID) );

  //////////////////////////////////////
  // Register uniform properties
  //
  //
  shader.SetUniform( "uBlurTexCoordScale", 0.125f );
  shader.SetUniform( "uGeometryStretchFactor", 0.05f );
  shader.SetUniform( "uSpeedScalingFactor", 0.5f );
  shader.SetUniform( "uObjectFadeStart", Vector2( 0.25f, 0.25f ) );
  shader.SetUniform( "uObjectFadeEnd", Vector2( 0.5f, 0.5f ) );
  shader.SetUniform( "uAlphaScale", 0.75f );
  shader.SetUniform( "uNumSamples", static_cast<float>( numBlurSamples ) );
  shader.SetUniform( "uRecipNumSamples", 1.0f / static_cast<float>( numBlurSamples ) );
  shader.SetUniform( "uRecipNumSamplesMinusOne", 1.0f / static_cast<float>( numBlurSamples - 1.0f ) );
  shader.SetUniform( "uModelLastFrame", Matrix::IDENTITY );

  return shader;
}

}

}

#endif //#ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_BLUR_H__