WebGL:使用两个着色器,第一个的输出作为第二个的输入,仅看到第二个的输出

时间:2018-08-20 18:23:07

标签: javascript glsl webgl shader

我怀疑这对绑定的含义是一种误解,但是我对我在这里做错的事情不知所措。我已经在帖子的末尾添加了相关代码。

我正在努力在GPU上实现数值算法。具体来说,我正在关注Nvidia的this example。特别是,该算法的一部分使用了迭代技术,其中一次迭代的输出用作下一次迭代的输入。在这里做出决策时,我特别关注的是第38.3.1节。

现在,很多事情都在为我学习WebGL / OpenGL / GLSL,所以我不会直接学习。在这一点上,我只是想通过在一个着色器中渲染图像来直接模拟一个“迭代” (仅是统一的颜色)到帧缓冲区,将输出复制到另一个纹理,并将该第二个纹理作为统一的输入传递给第二个着色器。然后,第二个着色器应在图像上添加一个高斯点,并再次渲染到与第一个着色器相同的帧缓冲区(覆盖原始帧)。然后,将第二个着色器的输出再次复制到辅助纹理,将其作为统一输入传递到最终着色器,以将所有内容呈现到屏幕。

我的问题:如果仅在第一个或第二个着色器上运行 ,则只能在屏幕上看到该阶段的预期输出。这告诉我着色器正在运行,并且正在按我的预期进行复制(因为最终的渲染到屏幕可以看到复制的纹理)。但是,如果我同时执行这两个步骤,则只能在屏幕上单独获得第二个着色器的输出(好像第一个着色器的输入仅为0),这告诉我由于某种原因,第二个着色器的统一输入没有得到我对第一个期望。

所有片段着色器都使用相同的顶点着色器,该顶点着色器仅接受解域的边界并传递位置的变化vec2。

相关代码如下。为了简洁起见,我没有包括着色器设置,但是基本上我创建了程序,然后获取统一/属性位置并将其存储在名称相似的属性中,然后激活属性。我还检查了程序是否成功链接。

最后一点:运行该控制台时,我没有看到警告或错误。

帧缓冲设置:

function initFramebuffers() {
    console.log("Creating framebuffer for flow field");
    flowFramebuffer = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, flowFramebuffer);
    frontTex = gl.createTexture();
    gl.activeTexture(gl.TEXTURE1);
    gl.bindTexture(gl.TEXTURE_2D, frontTex);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, nx, ny, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, frontTex, 0);
    // Start by zeroing out the flow field
    gl.clearColor(0.0,0.0,0.0,0.0);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    // Now create the texture for the flow field at the last step
    backTex = gl.createTexture();
    gl.activeTexture(gl.TEXTURE2);
    gl.bindTexture(gl.TEXTURE_2D, backTex);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, nx, ny, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
    gl.copyTexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 0, 0, nx, ny, 0); // Copy the blank flow field in to our back texture
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
}

阶段1:

function stage1() {
    console.log("Stage 1...");
    gl.useProgram(1Program);
    gl.bindFramebuffer(gl.FRAMEBUFFER,flowFramebuffer);
    gl.activeTexture(gl.TEXTURE1); // We're going to draw this result to texture unit 1
    gl.viewport(0,0, nx, ny);
    gl.bindBuffer(gl.ARRAY_BUFFER, solutionGrid);
    gl.vertexAttribPointer(stage1program.vertexPositionAttribute, solutionGrid.itemSize, gl.FLOAT, false, 0, 0);
    gl.uniform1i(stage1program.flowVelUniform, 2); // Use the texture in unit2 as the flowField uniform (unit1 is our current/updating texture)
    gl.uniform1i(stage1program.inFieldUniform, 2); // We're self-advecting, so use the same texture here.
    gl.uniform1f(stage1program.dtUniform, 1.0/60.0); // 60 frames per second
    gl.drawArrays(gl.TRIANGLES, 0, solutionGrid.numItems); // Solve
    gl.activeTexture(gl.TEXTURE2); // Now copy the framebuffer in to texture2
    gl.copyTexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 0, 0, nx, ny, 0);
    gl.bindFramebuffer(gl.FRAMEBUFFER,null);
}

stage1的着色器:

precision mediump float;
uniform float dt;
uniform sampler2D toAdvect; // Input dye field, varies 0 (no dye) to 1 (filled with dye)
uniform sampler2D flowField; // Flow field from the flow calculation step
varying vec2 vertexOut; // The location of the vertex [-1,1]

vec2 simToTextureSpace(vec2 vertex) {
    return 0.5*(vertex+1.0);
}

void main() {
    gl_FragColor = vec4(0.0,0.4,0.6,1.0);
}

阶段2:

function stage2() {
    gl.useProgram(stage2program);
    gl.bindFramebuffer(gl.FRAMEBUFFER,flowFramebuffer);
    gl.activeTexture(gl.TEXTURE1); // We're going to draw this result to texture unit 1
    gl.viewport(0,0, nx, ny);
    gl.bindBuffer(gl.ARRAY_BUFFER, solutionGrid);
    gl.vertexAttribPointer(stage2program.vertexPositionAttribute, solutionGrid.itemSize, gl.FLOAT, false, 0, 0);
    gl.uniform1i(stage2program.flowVelUniform, 2); // Use the texture in unit2 as the flowField uniform (unit1 is our current/updating texture)
    gl.uniform1f(stage2program.dtUniform, 1.0/60.0); // 60 frames per second
    gl.drawArrays(gl.TRIANGLES, 0, solutionGrid.numItems); // Solve
    gl.activeTexture(gl.TEXTURE2); // Now copy out
    gl.copyTexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 0, 0, nx, ny, 0);
    gl.bindFramebuffer(gl.FRAMEBUFFER,null);
}

第2阶段着色器:

precision mediump float;
uniform float dt;
uniform sampler2D flowField; // Flow field from the flow calculation step
varying vec2 vertexOut; // The location of the vertex [-1,1]

vec2 simToTextureSpace(vec2 vertex) {
    return 0.5*(vertex+1.0);
}

void main() {
    vec2 texPosition = simToTextureSpace(vertexOut);
    vec4 last = texture2D(flowField, texPosition);
    float radius2 = pow(vertexOut.x,2.0)+pow(vertexOut.y,2.0);
    gl_FragColor = last+vec4(60.0*dt*exp(-radius2/0.001),0.0,0.0,1.0);
}

渲染到屏幕:

function drawScene() {
        // console.log("Drawing scene");
        gl.useProgram(visualProgram);
        gl.activeTexture(gl.TEXTURE0);
        gl.viewport(0,0, gl.viewportWidth, gl.viewportHeight);
        gl.clearColor(0.0,0.0,1.0,1.0); // Clear to blue
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
        gl.bindBuffer(gl.ARRAY_BUFFER, solutionGrid); // Just reuse the coordinates from the fluid position buffer
        gl.vertexAttribPointer(visualProgram.vertexPositionAttribute, solutionGrid.itemSize, gl.FLOAT, false, 0, 0);
        gl.uniform1i(visualProgram.inFieldUniform, 2);
        gl.drawArrays(gl.TRIANGLES, 0, solutionGrid.numItems);
}

渲染到屏幕着色器:

precision mediump float;
uniform sampler2D inField; // field to draw
varying vec2 vertexOut; // The location of the vertex [-1,1]

vec2 simToTextureSpace(vec2 vertex) {
    return 0.5*(vertex+1.0);
}

void main() {
    vec2 texPosition = simToTextureSpace(vertexOut);
    vec4 drawField = texture2D(inField,texPosition);

    gl_FragColor = drawField;
}

通话顺序:

// Setup shaders, initFramebuffers(), etc
//console.log("Drawing...");
stage1();
stage2();
drawScene();

1 个答案:

答案 0 :(得分:1)

结果表明,在其中某个地方我犯了一个错误,并且在引用统一输入时使用了稍微不同的对象名称。 I.E

myObject.uniformVal

vs

myObject.uniformVel

这一定是完全偶然的,但是所显示的错误并未导致抛出实际错误。它现在正在工作,因此,如果其他任何人遇到类似问题,请检查您的参数名称:)