#ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_STRETCH_H__
#define __DALI_TOOLKIT_SHADER_EFFECT_MOTION_STRETCH_H__
/*
* Copyright (c) 2016 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
#include
#include
#include
// INTERNAL INCLUDES
#include
namespace Dali
{
namespace Toolkit
{
/**
* @brief Set the properties for the motion stretch
*/
inline void SetMotionStretchProperties( Actor& actor )
{
actor.RegisterProperty( "uGeometryStretchFactor", 0.5f );
actor.RegisterProperty( "uSpeedScalingFactor", 0.5f );
actor.RegisterProperty( "uObjectFadeStart", Vector2( 0.25f, 0.25f ) );
actor.RegisterProperty( "uObjectFadeEnd", Vector2( 0.5f, 0.5f ) );
actor.RegisterProperty( "uAlphaScale", 0.75f );
Property::Index uModelProperty = actor.RegisterProperty( "uModelLastFrame", Matrix::IDENTITY );
Constraint constraint = Constraint::New( actor, uModelProperty, EqualToConstraint() );
constraint.AddSource( Source( actor , Actor::Property::WORLD_MATRIX ) );
constraint.Apply();
}
/**
* @brief Creates a new MotionStretchEffect
*
* Motion stretch shader works on a per object basis. Objects will stretch in the direction of motion when they move, or if the camera moves.
*
* Animatable/Constrainable uniforms:
* "uGeometryStretchFactor" - This scales the amount the geometry stretches along the motion velocity vector.
* A smaller value means the geometry stretches less, larger it stretches more. Default 0.5.
* "uSpeedScalingFactor" - This value is 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 stretched 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 Vector2(0.25, 0.25), which is half way towards the edge for
* an ImageVisual::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 stretched 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 ImageVisual::QUAD.
* "uAlphaScale" - Global scaler applied to the alpha of the actor. Used to make the stretched actor a bit more subtle
* 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.
* "uModelLastFrame" - The model to world space transformation matrix of the actor in the previous frame.
*
* @return The newly created Property::Map with the motion stretch effect
*/
inline Property::Map CreateMotionStretchEffect()
{
std::string vertexSource;
vertexSource =
"precision mediump float;\n"
"attribute vec2 aPosition;\n"
"uniform mat4 uMvpMatrix;\n"
"uniform mat4 uModelView;\n"
"uniform mat4 uViewMatrix;\n"
"uniform mat4 uProjection;\n"
"uniform vec3 uSize;\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"
"varying vec2 vTexCoord;\n"
"void main()\n"
"{\n"
// get view space position of vertex this frame and last frame
" vec4 vertexPosition = vec4(aPosition, 0.0, 1.0);\n"
" vertexPosition.xyz *= uSize;\n"
" vec4 viewSpaceVertex = uModelView * vertexPosition;\n"
" vec4 viewSpaceVertexLastFrame = uViewMatrix * uModelLastFrame * vertexPosition;\n"
// work out vertex's last movement in view space
" vec3 viewSpacePosDelta = viewSpaceVertex.xyz - viewSpaceVertexLastFrame.xyz;\n"
" float reciprocalTimeDelta = 1.0 / timeDelta;\n"
// get clip space position of vertex this frame and last frame
" vec4 clipSpaceVertex = uMvpMatrix * vertexPosition;\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, 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
// We raise t to a power in order that non-trailing vertices are effected much more than trailing ones
// 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 * t * 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 = viewSpaceVertex.xy;\n"
" vec2 texCoord = aPosition + vec2(0.5);"
" vTexCoord = texCoord;\n"
"}\n";
std::string fragmentSource;
fragmentSource =
"precision mediump float;\n"
"uniform sampler2D sTexture;\n"
"uniform vec4 uColor;\n"
"uniform vec2 uObjectFadeStart;\n"
"uniform vec2 uObjectFadeEnd;\n"
"uniform float uAlphaScale;\n"
// inputs
"varying vec2 vModelSpaceCenterToPos;\n"
"varying vec2 vScreenSpaceVelocityVector;\n"
"varying float vSpeed;\n"
"varying vec2 vTexCoord;\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 stretched object and the 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
// standard actor texel
" vec4 colActor = texture2D(sTexture, vTexCoord);\n"
" gl_FragColor = colActor;\n"
" gl_FragColor.a *= fadeToEdgesScale;\n" // fade actor to its edges based on speed of motion
" gl_FragColor *= uColor;\n"
"}";
Property::Map map;
Property::Map customShader;
customShader[ Visual::Shader::Property::VERTEX_SHADER ] = vertexSource;
customShader[ Visual::Shader::Property::FRAGMENT_SHADER ] = fragmentSource;
customShader[ Visual::Shader::Property::SUBDIVIDE_GRID_X ] = 10;
customShader[ Visual::Shader::Property::SUBDIVIDE_GRID_Y ] = 10;
customShader[ Visual::Shader::Property::HINTS ] = Shader::Hint::OUTPUT_IS_TRANSPARENT;
map[ Visual::Property::SHADER ] = customShader;
return map;
}
}
}
#endif //#ifndef __DALI_TOOLKIT_SHADER_EFFECT_MOTION_STRETCH_H__