c++ - OpenGL - 翻译拉伸(stretch)和扭曲 Sprite

Question

我正在松散地遵循 opengl-tutorial.org 上非常方便的教程.我已经能够创建一个网格，为它绘制一个 Sprite ，然后完美地旋转和缩放该网格。

但是，我在尝试平移网格时遇到了一些问题。 (下图)

这是 Sprite 的更新函数:

    Transform* transform = static_cast<Transform*>(owner->GetComponent(CID_TRANSFORM));

    glUseProgram(shaderID_);

    glm::mat4 projection = glm::perspective(45.0f , 4.0f / 3.0f, 0.1f, 100.0f);

    glm::mat4 view = glm::lookAt(
        glm::vec3(3, 3, 3),
        glm::vec3(0, 0, 0),
        glm::vec3(0, 1, 0)
        );

    glm::mat4 model = transform->GetModelMatrix();

    glm::mat4 mvp = projection * view * model;

    GLuint matrixID = glGetUniformLocation(shaderID_, "MVP");

    glUniformMatrix4fv(matrixID, 1, GL_FALSE, &mvp[0][0]);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texture_);
    glUniform1i(samplerID_, 0);

    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer_);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);

    glEnableVertexAttribArray(1);
    glBindBuffer(GL_ARRAY_BUFFER, uvBuffer_);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);

    glDrawArrays(GL_TRIANGLES, 0, 3 * 2);

    glDisableVertexAttribArray(0);
    glDisableVertexAttribArray(1);

这里是 getModelMatrix 函数:

glm::mat4 Transform::GetModelMatrix()
{
    glm::mat4 trans = glm::mat4(
        1.0f, 0.0f, 0.0f, translation.x,
        0.0f, 1.0f, 0.0f, translation.y,
        0.0f, 0.0f, 1.0f, translation.z,
        0.0f, 0.0f, 0.0f, 1.0f);

    float xCos = glm::cos(rotation.x);
    float xSin = glm::sin(rotation.x);
    float yCos = glm::cos(rotation.y);
    float ySin = glm::sin(rotation.y);
    float zCos = glm::cos(rotation.z);
    float zSin = glm::sin(rotation.z);

    glm::mat4 xRotation = glm::mat4(
        1.0f, 0.0f, 0.0f, 0.0f,
        0.0f, xCos, -xSin, 0.0f,
        0.0f, xSin, xCos, 0.0f,
        0.0f, 0.0f, 0.0f, 1.0f);

    glm::mat4 yRotation = glm::mat4(
        yCos, 0.0f, ySin, 0.0f,
        0.0f, 1.0f, 0.0f, 0.0f,
        -ySin, 0.0f, yCos, 0.0f,
        0.0f, 0.0f, 0.0f, 1.0f);

    glm::mat4 zRotation = glm::mat4(
        zCos, -zSin, 0.0f, 0.0f,
        zSin, zCos, 0.0f, 0.0f,
        0.0f, 0.0f, 1.0f, 0.0f,
        0.0f, 0.0f, 0.0f, 1.0f);

    glm::mat4 rot = xRotation * yRotation * zRotation;

    glm::mat4 sca = glm::mat4(
        scale.x, 0.0f, 0.0f, 0.0f,
        0.0f, scale.y, 0.0f, 0.0f,
        0.0f, 0.0f, scale.z, 0.0f,
        0.0f, 0.0f, 0.0f, 1.0f);

    return trans * rot * sca;
}

这是从 (3, 3, 3) 看原点的 Sprite 。

这是从 (3, 3, 3) 观察到的转换为 (1, 0, 0) 的 Sprite 。

Answer 1

与 OpenGL 相匹配，GLM 以列主要顺序存储矩阵。构造函数还期望以相同的顺序指定元素。

但是，您的翻译矩阵是按行主要顺序指定的:

glm::mat4 trans = glm::mat4(
    1.0f, 0.0f, 0.0f, translation.x,
    0.0f, 1.0f, 0.0f, translation.y,
    0.0f, 0.0f, 1.0f, translation.z,
    0.0f, 0.0f, 0.0f, 1.0f);

要以正确的列主顺序指定矩阵，这需要:

glm::mat4 trans = glm::mat4(
    1.0f, 0.0f, 0.0f, 0.0f,
    0.0f, 1.0f, 0.0f, 0.0f,
    0.0f, 0.0f, 1.0f, 0.0f,
    translation.x, translation.y, translation.z, 1.0f);