c++ - opengl - framebuffer 纹理剪裁得比我设置的小？

Question

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屏幕外渲染(一些简单的元球)，然后将该纹理渲染到主后台缓冲区。

一切看起来都很棒，除了纹理出现剪裁，即。它不是完整的窗口尺寸(一个轴上缺少大约 128 像素)。这是屏幕截图:http://tinypic.com/r/9telwg/7

有什么想法会导致这种情况吗？我读了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) 而我的窗口是 768x1024。它也仍然有点剪裁，因为我似乎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，然后在我完成时调用 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。我没有在任何地方找到这个例子，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(viewport)都在变化。通过手动将每个设置为 1024x768(我选择使用常量)，变形球以适当的纵横比在屏幕外正确渲染。它们的 1024x1024 纹理被渲染为广告牌，纵横比漂亮而清晰。完成后，我将它们恢复为应用程序其余部分使用的状态。下面是工作代码:

#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);

}

Answer 1

您是否根据纹理的大小设置视口(viewport)？我没有在您的代码中找到任何视口(viewport)设置...