Question

我正试着用草纹理地面。有人会介意通过我的步骤来获得2D纹理以显示在3D空间中吗？我对在线教程没有任何好运。

这是我的步骤：

1）调用sprite类初始化来设置顶点坐标和uv数据

void Sprite::init(vec3 bottomleft, vec3 topLeft, vec3 topRight, vec3 bottomRight, std::string texturePath)
{

    _texture = ImageLoader::loadPNG(texturePath);

    _points = { bottomleft.x, bottomleft.y, bottomleft.z, topLeft.x, topLeft.y, topLeft.z, topRight.x, topRight.y, topRight.z, topRight.x, topRight.y, topRight.z, bottomRight.x, bottomRight.y, bottomRight.z, bottomleft.x, bottomleft.y, bottomleft.z };
    _uv = { 0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f };

}

我使用均匀采样器并激活纹理

    //draw ground texture
    glUniform1i(samplerLocation, 0);
    glActiveTexture(GL_TEXTURE0);
    _grassTexture.draw();

draw函数实现如下，它将数据放入缓冲区并绘制三角形：

    void Sprite::draw()
    {
        if (_vboID == 0)
        {
            glGenBuffers(1, &_vboID);
        }

        glBindTexture(GL_TEXTURE_2D, _texture.id);

        glBindBuffer(GL_ARRAY_BUFFER, _vboID);
        glBufferData(GL_ARRAY_BUFFER, _points.size() * sizeof(float) + _uv.size() * sizeof(float), nullptr, GL_STATIC_DRAW);
        glBufferSubData(GL_ARRAY_BUFFER, 0, _points.size() * sizeof(float), &_points.front());
        glBufferSubData(GL_ARRAY_BUFFER, _points.size() * sizeof(float), _uv.size() * sizeof(float), &_uv.front());

        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(1);

        //position attribute pointer
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, &_points.front());

        //uv attribute pointer
        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, &_uv.front());

        glDrawArrays(GL_TRIANGLES, 0, 6);

        glDisableVertexAttribArray(0);
        glDisableVertexAttribArray(1);

        glBindBuffer(GL_ARRAY_BUFFER, 0);
    }

顶点着色器：

#version 400

in vec4 vertexPosition;
in vec2 vertexUV;

out vec4 fragmentColor;
out vec2 fragmentUV;

uniform mat4 MVP;
uniform vec4 COLOR;

void main()
{
    gl_Position = MVP * vertexPosition;
    fragmentColor = COLOR;
    fragmentUV = vec2(vertexUV.x, 1.0 - vertexUV.y);
}

和片段着色器：

#version 400

in vec4 fragmentColor;
in vec2 fragmentUV;

out vec4 fragColor;

uniform sampler2D SAMPLER;

void main()
{
    vec4 textureColor = texture(SAMPLER, fragmentUV);
    fragColor = textureColor * fragmentColor;
}

此时，屏幕上不显示任何内容。我知道片段着色器中的textureColor是绿色的，所以看起来正确设置了制服。我最好的猜测是我要么缺少纹理初始化步骤，要么没有正确填充缓冲区。

Answer 1

我认为调用glVertexAttribPointer时指针参数存在问题。您正在传递_points和_uv数组的地址，但是您应该相对于vbo的基数传递偏移量。

尝试：

    //position attribute pointer
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

    //uv attribute pointer
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid*)(_points.size() * sizeof(float)));

OpenGL纹理着色器无法显示到屏幕

1 个答案: