opengl - 比我设置的更小的帧缓冲纹理？

Posted 2023-03-23

【中文标题】opengl - 比我设置的更小的帧缓冲纹理？

【英文标题】：opengl - framebuffer texture clipped smaller than I set it?

【发布时间】：2011-12-06 14:48:51

【问题描述】：

我正在使用 opengl ES 2.0 我正在使用链接到纹理的帧缓冲区来编译（一些简单的元球的）屏幕外渲染，然后将该纹理渲染到主后台缓冲区。

一切看起来都很棒，除了纹理看起来被剪裁了，即。它不是完整的窗口尺寸（一个轴上缺少大约 128 个像素）。截图如下：http://tinypic.com/r/9telwg/7

有什么想法会导致这种情况吗？我阅读here 将glViewport 设置为纹理的大小，但这给了我不同的纵横比，因为纹理metaballsTexture 是正方形（1024x1024）并且我的窗口是768x1024。它也仍然有点剪裁，因为看起来我无法让帧缓冲区足够大，即使纹理大于我的窗口大小。下面是我的代码。当我准备好时，我在渲染期间调用 PrepareToAddMetaballs()，然后连续调用 AddMetaball，现在渲染到我的屏幕外 FBO，然后在我完成后调用 FinishedAddingMetaballs，然后调用 Render() 以显示链接到 FBO 的屏幕外纹理到主后台缓冲区。

#include "Metaballs.h"
#include "s3e.h"
#include "IwGL.h"
#include "Render.h"
#include "vsml.h"
#include <vector>
#include <string>
#include <iostream>
#include "1013Maths.h"

#define GL_RGBA8 0x8058

MetaBalls::MetaBalls() : metaballsTexture(NULL), metaballsShader(NULL) 
    glGenFramebuffers(1, &myFBO);

    metaballTexture[0] = NULL;
    metaballTexture[1] = NULL;
    metaballTexture[2] = NULL;
    CRender::Instance()->CreateTexture("WaterCanvas.png", &metaballsTexture);
    CRender::Instance()->CreateTexture("metaball.pvr", &metaballTexture[0]);
    CRender::Instance()->CreateTexture("metaball-1.png", &metaballTexture[1]);
    CRender::Instance()->CreateTexture("metaball-2.png", &metaballTexture[2]);
    CRender::Instance()->CreateShader("Shaders/metaballs.fs", "Shaders/metaballs.vs", &metaballsShader);

    glBindFramebuffer(GL_FRAMEBUFFER, myFBO);
    // Attach texture to frame buffer
    glBindTexture(GL_TEXTURE_2D, metaballsTexture->m_id);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, metaballsTexture->m_id, 0);
    glClearColor(1,1,1,0);
    glClear(GL_COLOR_BUFFER_BIT);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) 
        std::string error = "Metaballs framebuffer incomplete";
        std::cerr << error << std::endl;
        throw error;
    

    float w = PTM_DOWNSCALE(float(metaballsTexture->GetWidth()));
    float h = PTM_DOWNSCALE(float(metaballsTexture->GetHeight()));

    CRender::Instance()->BuildQuad(
        tVertex( b2Vec3(0,0,0), b2Vec2(0,1) ),
        tVertex( b2Vec3(w,0,0), b2Vec2(1,1) ),
        tVertex( b2Vec3(w,h,0), b2Vec2(1,0) ),
        tVertex( b2Vec3(0,h,0), b2Vec2(0,0) ),
        buffer);



MetaBalls::~MetaBalls() 
    CRender::Instance()->ReleaseShader(metaballsShader);
    CRender::Instance()->ReleaseTexture(metaballsTexture);
    CRender::Instance()->ReleaseTexture(metaballTexture[0]);
    CRender::Instance()->ReleaseTexture(metaballTexture[1]);
    CRender::Instance()->ReleaseTexture(metaballTexture[2]);
    glDeleteFramebuffers(1, &myFBO);


void MetaBalls::PrepareToAddMetaballs(b2Vec3& paintColour) 

    // bind render to texture
    glBindFramebuffer(GL_FRAMEBUFFER, myFBO);
    // Set our viewport so our texture isn't clipped (appears stretched and clipped)
    // glViewport(0, 0, metaballsTexture->GetWidth(), metaballsTexture->GetHeight());
    glClearColor(paintColour.x, paintColour.y, paintColour.z, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);



void MetaBalls::FinishedAddingMetaballs() 
    glBindFramebuffer(GL_FRAMEBUFFER, NULL);
    // CRender::Instance()->SetWindowViewport();


void MetaBalls::AddMetaball(float x, float y, uint size) 

    // render the metaball texture to larger texture
    VSML::setIdentityMatrix(pTransform);
    pTransform[12] = PTM_DOWNSCALE(x);
    pTransform[13] = PTM_DOWNSCALE(y+4); // the +4 is for a bit of overlap with land
    float oldview[16];
    float identity[16];
    VSML::setIdentityMatrix(identity);
    memcpy(oldview, CRender::Instance()->GetViewMatrix(), sizeof(float)*16);
    memcpy(CRender::Instance()->GetViewMatrix(),identity, sizeof(float)*16);
    CRender::Instance()->DrawSprite(metaballTexture[size], pTransform, 1.0f, true);
    memcpy(CRender::Instance()->GetViewMatrix(),oldview, sizeof(float)*16);


void MetaBalls::Render() 

    VSML::setIdentityMatrix(pTransform);
    pTransform[12] = PTM_DOWNSCALE(-128);
    pTransform[13] = PTM_DOWNSCALE(-256);

    // render our metaballs texture using alpha test shader
    CRender::Instance()->BindShader(metaballsShader);
    CRender::Instance()->BindTexture(0, metaballsTexture);

    CRender::Instance()->SetMatrix(metaballsShader, "view", CRender::Instance()->GetViewMatrix());
    CRender::Instance()->SetMatrix(metaballsShader, "world", pTransform);
    CRender::Instance()->SetMatrix(metaballsShader, "proj", CRender::Instance()->GetProjMatrix());

    CRender::Instance()->SetBlending(true);
    CRender::Instance()->DrawPrimitives(buffer);
    CRender::Instance()->SetBlending(false);

=====================

编辑

啊哈！知道了。我在任何地方都没有找到这个例子，但我通过调整透视矩阵来修复它。它在工作时设置为 1024x768，但窗口大小为 768x1024，投影矩阵和视口都在变化。通过手动将每个设置为 1024x768（我选择使用常量），元球以适当的纵横比正确呈现在屏幕外。他们的 1024x1024 纹理被渲染为一个广告牌，其纵横比又好又锐利。完成后，我将它们恢复为应用程序其余部分使用的内容。以下是工作代码：

#include "Metaballs.h"
#include "s3e.h"
#include "IwGL.h"
#include "Render.h"
#include "vsml.h"
#include <vector>
#include <string>
#include <iostream>
#include "1013Maths.h"

MetaBalls::MetaBalls() : metaballsTexture(NULL), metaballsShader(NULL) 

    glGenFramebuffers(1, &myFBO);

    metaballTexture[0] = NULL;
    metaballTexture[1] = NULL;
    metaballTexture[2] = NULL;
    CRender::Instance()->CreateTexture("WaterCanvas.png", &metaballsTexture);
    CRender::Instance()->CreateTexture("metaball.pvr", &metaballTexture[0]);
    CRender::Instance()->CreateTexture("metaball-1.png", &metaballTexture[1]);
    CRender::Instance()->CreateTexture("metaball-2.png", &metaballTexture[2]);
    CRender::Instance()->CreateShader("Shaders/metaballs.fs", "Shaders/metaballs.vs", &metaballsShader);

    glBindFramebuffer(GL_FRAMEBUFFER, myFBO);

    // Attach texture to frame buffer
    glBindTexture(GL_TEXTURE_2D, metaballsTexture->m_id);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, metaballsTexture->m_id, 0);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) 
        std::string error = "Metaballs framebuffer incomplete";
        std::cerr << error << std::endl;
        throw error;
    

    float w = PTM_DOWNSCALE(float(metaballsTexture->m_width));
    float h = PTM_DOWNSCALE(float(metaballsTexture->m_height));

    CRender::Instance()->BuildQuad(
        tVertex( b2Vec3(0,0,0), b2Vec2(0,1) ),
        tVertex( b2Vec3(w,0,0), b2Vec2(1,1) ),
        tVertex( b2Vec3(w,h,0), b2Vec2(1,0) ),
        tVertex( b2Vec3(0,h,0), b2Vec2(0,0) ),
        buffer);

    // return to default state
    glBindFramebuffer(GL_FRAMEBUFFER, 0);


MetaBalls::~MetaBalls() 
    CRender::Instance()->ReleaseShader(metaballsShader);
    CRender::Instance()->ReleaseTexture(metaballsTexture);
    CRender::Instance()->ReleaseTexture(metaballTexture[0]);
    CRender::Instance()->ReleaseTexture(metaballTexture[1]);
    CRender::Instance()->ReleaseTexture(metaballTexture[2]);
    glDeleteFramebuffers(1, &myFBO);


void MetaBalls::PrepareToAddMetaballs(b2Vec3& paintColour) 

    // bind render to texture
    glBindFramebuffer(GL_FRAMEBUFFER, myFBO);

    // Set orthographic projection
    cfloat w = SCREEN_WIDTH / PTM_RATIO;
    cfloat h = SCREEN_HEIGHT / PTM_RATIO;
    VSML::ortho(-w, 0, -h, 0, 0.0f, -1.0f, CRender::Instance()->m_Proj);

    // Set our viewport so our texture isn't clipped
    glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
    glClearColor(paintColour.x, paintColour.y, paintColour.z, 0.1f);
    glClear(GL_COLOR_BUFFER_BIT);



void MetaBalls::FinishedAddingMetaballs() 
    glBindFramebuffer(GL_FRAMEBUFFER, NULL);
    CRender::Instance()->SetWindowViewport();


void MetaBalls::AddMetaball(float x, float y, uint size) 

    // render the metaball texture to larger texture
    VSML::setIdentityMatrix(pTransform);
    pTransform[12] = PTM_DOWNSCALE(x);
    pTransform[13] = PTM_DOWNSCALE(y);
    float oldview[16];
    float identity[16];
    VSML::setIdentityMatrix(identity);
    memcpy(oldview, CRender::Instance()->GetViewMatrix(), sizeof(float)*16);
    memcpy(CRender::Instance()->GetViewMatrix(),identity, sizeof(float)*16);
    CRender::Instance()->DrawSprite(metaballTexture[size], pTransform, 1.0f, true);
    memcpy(CRender::Instance()->GetViewMatrix(),oldview, sizeof(float)*16);


void MetaBalls::Render() 

    VSML::setIdentityMatrix(pTransform);
    pTransform[12] = PTM_DOWNSCALE(0);
    pTransform[13] = PTM_DOWNSCALE(-256);

    // render our metaballs texture using alpha test shader
    CRender::Instance()->BindShader(metaballsShader);
    CRender::Instance()->BindTexture(0, metaballsTexture);

    CRender::Instance()->SetMatrix(metaballsShader, "view", CRender::Instance()->GetViewMatrix());
    CRender::Instance()->SetMatrix(metaballsShader, "world", pTransform);
    CRender::Instance()->SetMatrix(metaballsShader, "proj", CRender::Instance()->GetProjMatrix());

    CRender::Instance()->SetBlending(true);
    CRender::Instance()->DrawPrimitives(buffer);
    CRender::Instance()->SetBlending(false);

【问题讨论】：

我已经设法通过在渲染时将变换 x 和 y 设置为 0 来使其在 1024x768 中全部可见，但是如果我将窗口设置为 768x1024，它的底部会被剪裁（256 像素我想）。我认为这是因为我仍在水平方向绘制它，但我将视图矩阵旋转了 90 度（当 ipad 旋转时）。所以看起来屏幕外渲染的部分被剪掉了？这是因为视口吗？

【参考方案1】：

您是否根据纹理的大小设置视口？我没有在您的代码上找到任何视口设置...

【讨论】：

嗨，是的，你可以看到我已经在 PrepareToAddMetaballs 函数中尝试过这个，它目前被注释掉了，虽然它只是稍微向宽度方向拉伸纹理，但剪裁问题仍然存在。跨度>

你设置透视矩阵了吗？

我刚刚发现一个帖子有同样的问题，但没有解决方案，这可能有助于澄清。 ***.com/questions/5041098/…

透视矩阵也需要调整，见上。对于那些阅读，还要注意它在工作时看起来分辨率很差，因此有必要调整我的 metaballs 着色器中的容差。不知道为什么会这样，但在我调整后它实现了清晰的每像素抗锯齿。

由于同样的问题，我花了 1 小时了解图像后处理有什么问题。