菜鸟教程小白 发表于 2022-12-13 04:10:54

ios - OpenGL-ES:选择性混合


                                            <p><p>我正在使用 GPUImage 的角点检测器从相机捕获的帧中提取角点。我想在角落坐标处渲染 Spark 。当我得到角坐标后，我将它传递给我的 Spark 生成器(非常类似于 GPUImage 的十字准线生成器):</p>

<pre><code>public func renderSparkles(_ positions:) {
    imageFramebuffer.activateFramebufferForRendering()
    imageFramebuffer.timingStyle = .stillImage

    glEnable(GLenum(GL_POINT_SPRITE_OES))

    sparklesShader.use()
    uniformSettings.restoreShaderSettings(sparklesShader)

    clearFramebufferWithColor(Color.transparent)

    guard let positionAttribute = sparklesShader.attributeIndex(&#34;position&#34;) else {
         fatalError(&#34;A position attribute was missing from the shader program during rendering.&#34;)
    }

    let convertedPositions = positions.flatMap{$0.toGLArray()}
    glVertexAttribPointer(positionAttribute, 2, GLenum(GL_FLOAT), 0, 0, convertedPositions)
    glDrawArrays(GLenum(GL_POINTS), 0, GLsizei(positions.count))

    notifyTargets()
}
</code></pre>

<p>在生成器的片段着色器中，我在角坐标处绘制闪光:</p>

<pre><code>uniform lowp vec3 crosshairColor;
varying highp vec2 centerLocation;

void main()
{
   lowp vec2 distanceFromCenter = abs(centerLocation - gl_PointCoord.xy);

   lowp float r = length(distanceFromCenter)*0.042;
   lowp float a = atan(distanceFromCenter.y,distanceFromCenter.x);      
   lowp float f = abs(cos(a*2.0))*0.100*-0.322/0.224;
   lowp float b = abs(cos(a*2.0))*0.078*-0.882/17.088;
   lowp float c = abs(cos(a*2.0))*0.030*-0.178*0.688;

   lowp vec4 color = vec4(1.0-smoothstep(f,b+0.04,r)) + vec4(1.0-smoothstep(b,c+0.02,r/0.644)) + vec4(1.0-smoothstep(b,c+0.011,r/0.764));
   gl_FragColor = color;
}
</code></pre>

<p> <a href="/image/LmOZS.png" rel="noreferrer noopener nofollow">Here is an example of output I&#39;ve got</a> </p>

<p>我怎样才能混合闪光？</p></p>
                                    <br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
                                            <p><p>如果其他人觉得有帮助，这里是基于 Rabbid76 建议的渲染 sparkles 方法的代码:</p>

<pre><code>public func renderSparkles(_ positions:) {
    imageFramebuffer.activateFramebufferForRendering()
    imageFramebuffer.timingStyle = .stillImage

    glEnable(GLenum(GL_POINT_SPRITE_OES))

    glEnable(GLenum(GL_BLEND))
    glBlendFunc(GLenum(GL_SRC_ALPHA),GLenum(GL_ONE_MINUS_CONSTANT_ALPHA))

    sparklesShader.use()
    uniformSettings.restoreShaderSettings(sparklesShader)

    clearFramebufferWithColor(Color.transparent)

    guard let positionAttribute = sparklesShader.attributeIndex(&#34;position&#34;) else {
      fatalError(&#34;A position attribute was missing from the shader program during rendering.&#34;)
    }

    let convertedPositions = positions.flatMap{$0.toGLArray()}
    glVertexAttribPointer(positionAttribute, 2, GLenum(GL_FLOAT), 0, 0, convertedPositions)
    glDrawArrays(GLenum(GL_POINTS), 0, GLsizei(positions.count))

    notifyTargets()   
}
</code></pre></p>
                                   
                                                <p style="font-size: 20px;">关于ios - OpenGL-ES:选择性混合，我们在Stack Overflow上找到一个类似的问题：
                                                        <a href="https://stackoverflow.com/questions/50157974/" rel="noreferrer noopener nofollow" style="color: red;">
                                                                https://stackoverflow.com/questions/50157974/
                                                        </a>
                                                </p>
                                       
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