我正在使用带有Metal的SceneKit。相机是固定的。 目标 当圆/敌人移动时,我希望它们具有运动模糊效果。当角色移动时,不应该有模糊效果。 计划 编写一个多通道SCNTechnique来处理这个问题,我认为这是实现我想要的效果的方法。 第一遍渲染:将敌人/圆形只渲染到另一个缓冲区 第二遍渲染:对此缓冲区应用运动模糊 第三遍渲染:用原始场景渲染运动模糊缓冲区。 附注:第二遍渲染会很棘手,因为我想象中每个对象都有自己的方向,而模糊效果也需要跟随移动。
因此,下面是我在SceneKit中设置对象的方式。
class Character : SCNNode
{
override init() {
super.init()
let img = UIImage(named: "texture1")!
material = SCNMaterial()
material.diffuse.contents = img
material.ambient.contents = img
let geometry = SCNSphere(radius: 40)
geometry.materials = [material]
self.categoryBitMask = 1
}
}
class Enemy : SCNNode
{
override init() {
super.init()
let img = UIImage(named: "texture2")!
material = SCNMaterial()
material.diffuse.contents = img
material.ambient.contents = img
let geometry = SCNSphere(radius: 40)
geometry.materials = [material]
self.categoryBitMask = 2
}
}
我可以将它们添加到场景中并且它们看起来不错。我可以使用SCNActions移动它们,它们的移动是正确的。
现在来讲一下我如何尝试运动模糊。
第一步
我想从这一步中仅提取敌人,因此该技术的这一部分看起来像下面这样,注意类别掩码只会为场景中的敌人绘制。
它将输出到我的自定义“enemiesColor”目标缓冲区。 注:DRAW_SCENE
<key>drawEnemies</key>
<dict>
<key>draw</key>
<string>DRAW_SCENE</string>
<key>includeCategoryMask</key>
<integer>2</integer>
<key>excludeCategoryMask</key>
<integer>1</integer>
<key>program</key>
<string>doesntexist</string>
<key>metalVertexShader</key>
<string>multi_vertex</string>
<key>metalFragmentShader</key>
<string>multi_fragment_vert</string>
<key>inputs</key>
<dict>
<key>colorSampler</key>
<string>COLOR</string>
<key>a_texcoord</key>
<string>a_texcoord-symbol</string>
<key>aPos</key>
<string>vertexSymbol</string>
</dict>
<key>outputs</key>
<dict>
<key>color</key>
<string>enemiesColor</string>
</dict>
</dict>
这个的金属渲染器如下所示:
#include <metal_stdlib>
using namespace metal;
#include <SceneKit/scn_metal>
struct custom_node_t3 {
float4x4 modelTransform;
float4x4 modelViewTransform;
float4x4 normalTransform;
float4x4 modelViewProjectionTransform;
};
struct custom_vertex_t
{
float4 position [[attribute(SCNVertexSemanticPosition)]];
float2 a_texcoord [[ attribute(SCNVertexSemanticTexcoord0) ]];
//SCNGeometrySourceSemanticTexcoord
};
constexpr sampler s = sampler(coord::normalized,
address::repeat,
filter::linear);
struct out_vertex_t
{
float4 position [[position]];
float2 texcoord;
};
vertex out_vertex_t multi_vertex(custom_vertex_t in [[stage_in]],
constant custom_node_t3& scn_node [[buffer(0)]])
{
out_vertex_t out;
out.texcoord = in.a_texcoord;
out.position = scn_node.modelViewProjectionTransform * float4(in.position.xyz, 1.0);
return out;
};
fragment half4 multi_fragment_vert(out_vertex_t vert [[stage_in]],
constant SCNSceneBuffer& scn_frame [[buffer(0)]],
texture2d<float, access::sample> colorSampler [[texture(0)]])
{
float4 FragmentColor = colorSampler.sample( s, vert.texcoord);
return half4(FragmentColor);
};
第二遍
我想要模糊“enemiesColor”缓冲区,目前它非常粗糙,所以我只是暂时使用高斯模糊技巧。
我将“enemiesColor”缓冲区作为输入并进行模糊处理,我将其输出为一个新的缓冲区:“enemyColor” 注意:DRAW_QUAD
这个通道的技术看起来像:
<key>blurEnemies</key>
<dict>
<key>draw</key>
<string>DRAW_QUAD</string>
<key>program</key>
<string>doesntexist</string>
<key>metalVertexShader</key>
<string>blur_vertex</string>
<key>metalFragmentShader</key>
<string>blur_fragment_vert</string>
<key>inputs</key>
<dict>
<key>colorSampler</key>
<string>COLOR</string>
<key>enemyColor</key>
<string>enemiesColor</string>
<key>a_texcoord</key>
<string>a_texcoord-symbol</string>
</dict>
<key>outputs</key>
<dict>
<key>color</key>
<string>chrisColor</string>
</dict>
</dict>
并且着色器是:
// http://rastergrid.com/blog/2010/09/efficient-gaussian-blur-with-linear-sampling/
constant float offset[] = { 0.0, 1.0, 2.0, 3.0, 4.0 };
constant float weight[] = { 0.2270270270, 0.1945945946, 0.1216216216, 0.0540540541, 0.0162162162 };
vertex out_vertex_t blur_vertex(custom_vertex_t in [[stage_in]],
constant custom_node_t3& scn_node [[buffer(0)]])
{
out_vertex_t out;
out.position = in.position;
out.texcoord = float2((in.position.x + 1.0) * 0.5 , (in.position.y + 1.0) * -0.5);
return out;
};
fragment half4 blur_fragment_vert(out_vertex_t vert [[stage_in]],
texture2d<float, access::sample> colorSampler [[texture(0)]],
texture2d<float, access::sample> enemyColor [[texture(1)]])
{
float4 enemySample = enemyColor.sample(s, vert.texcoord);
if (enemySample.a == 0)
{
//gl_LastFragData[0]
return half4(0.0 ,1.0 ,0.0, 0.5);
}
float4 FragmentColor = colorSampler.sample( s, vert.texcoord) * weight[0];
for (int i=1; i<5; i++) {
FragmentColor += colorSampler.sample( s, ( vert.texcoord + float2(0.0, offset[i])/224.0 ) ) * weight[i];
FragmentColor += colorSampler.sample( s, ( vert.texcoord - float2(0.0, offset[i])/224.0 ) ) * weight[i];
}
return half4(FragmentColor);
};
第三遍处理
当事情变得更加混乱时,我想将模糊的“enemyColor”缓冲器与原始场景一起应用。
我的第一个想法是,为什么不能只是叠加结果。我查看了混合模式,但没有找到合适的。
然后我想,也许我可以重新渲染场景,并将“enemyColor”和新的“color”缓冲器相加(如果这个方法即使在某种程度上起作用,可能有一些优化)。
注意:DRAW_SCENE
所以这个技巧就是:
<key>blendTogether</key>
<dict>
<key>draw</key>
<string>DRAW_SCENE</string>
<key>program</key>
<string>doesntexist</string>
<key>metalVertexShader</key>
<string>plain_vertex</string>
<key>metalFragmentShader</key>
<string>plain_fragment_vert</string>
<key>inputs</key>
<dict>
<key>colorSampler</key>
<string>COLOR</string>
<key>aPos</key>
<string>vertexSymbol</string>
<key>a_texcoord</key>
<string>a_texcoord-symbol</string>
</dict>
<key>outputs</key>
<dict>
<key>color</key>
<string>COLOR</string>
</dict>
</dict>
还有着色器(shader):
vertex out_vertex_t plain_vertex(custom_vertex_t in [[stage_in]],
constant SCNSceneBuffer& scn_frame [[buffer(0)]],
constant custom_node_t3& scn_node [[buffer(1)]])
{
out_vertex_t out;
out.position = scn_node.modelViewProjectionTransform * float4(in.position.xyz, 1.0);
out.texcoord = in.a_texcoord;
return out;
};
fragment half4 plain_fragment_vert(out_vertex_t vert [[stage_in]],
texture2d<float, access::sample> colorSampler [[texture(0)]])
{
float4 FragmentColor = colorSampler.sample( s, vert.texcoord);
return half4(FragmentColor);
};
在我的场景渲染结束后,我没有得到期望的效果。第一个问题是,这样的系统是否可能实现动态模糊效果?如果不可能,我就不想再浪费时间了。第二个问题是,我做错了什么?完成技巧如下:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>passes</key>
<dict>
<key>drawEnemies</key>
<dict>
<key>draw</key>
<string>DRAW_SCENE</string>
<key>includeCategoryMask</key>
<integer>2</integer>
<key>excludeCategoryMask</key>
<integer>1</integer>
<key>program</key>
<string>doesntexist</string>
<key>metalVertexShader</key>
<string>multi_vertex</string>
<key>metalFragmentShader</key>
<string>multi_fragment_vert</string>
<key>inputs</key>
<dict>
<key>colorSampler</key>
<string>COLOR</string>
<key>a_texcoord</key>
<string>a_texcoord-symbol</string>
<key>aPos</key>
<string>vertexSymbol</string>
</dict>
<key>outputs</key>
<dict>
<key>color</key>
<string>enemiesColor</string>
</dict>
</dict>
<key>blurEnemies</key>
<dict>
<key>draw</key>
<string>DRAW_QUAD</string>
<key>program</key>
<string>doesntexist</string>
<key>metalVertexShader</key>
<string>blur_vertex</string>
<key>metalFragmentShader</key>
<string>blur_fragment_vert</string>
<key>inputs</key>
<dict>
<key>colorSampler</key>
<string>COLOR</string>
<key>enemyColor</key>
<string>enemiesColor</string>
<key>a_texcoord</key>
<string>a_texcoord-symbol</string>
</dict>
<key>outputs</key>
<dict>
<key>color</key>
<string>chrisColor</string>
</dict>
</dict>
<key>blendTogether</key>
<dict>
<key>draw</key>
<string>DRAW_SCENE</string>
<key>program</key>
<string>doesntexist</string>
<key>metalVertexShader</key>
<string>plain_vertex</string>
<key>metalFragmentShader</key>
<string>plain_fragment_vert</string>
<key>inputs</key>
<dict>
<key>colorSampler</key>
<string>COLOR</string>
<key>aPos</key>
<string>vertexSymbol</string>
<key>a_texcoord</key>
<string>a_texcoord-symbol</string>
</dict>
<key>outputs</key>
<dict>
<key>color</key>
<string>COLOR</string>
</dict>
</dict>
</dict>
<key>sequence</key>
<array>
<string>blendTogether</string>
</array>
<key>targets</key>
<dict>
<key>enemiesColor</key>
<dict>
<key>type</key>
<string>color</string>
</dict>
<key>chrisColor</key>
<dict>
<key>type</key>
<string>color</string>
</dict>
</dict>
<key>symbols</key>
<dict>
<key>a_texcoord-symbol</key>
<dict>
<key>semantic</key>
<string>texcoord</string>
</dict>
<key>vertexSymbol</key>
<dict>
<key>semantic</key>
<string>vertex</string>
</dict>
</dict>
</dict>
</plist>