Transformations_练习二

尝试再次调用glDrawElements画出第二个箱子，只使用变换将其摆放在不同的位置。让这个箱子被摆放在窗口的左上角，并且会不断的缩放（而不是旋转）。（sin函数在这里会很有用，不过注意使用sin函数时应用负值会导致物体被翻转）

画图代码：

        //the first one
        // create transformations
        glm::mat4 transform = glm::mat4(1.0f); // make sure to initialize matrix to identity matrix first
        transform = glm::translate(transform, glm::vec3(0.5f, -0.5f, 0.0f));
        transform = glm::rotate(transform, (float)glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));

        // get matrix's uniform location and set matrix
        ourShader.use();
        unsigned int transformLoc = glGetUniformLocation(ourShader.ID, "transform");
        glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(transform));

        // render container
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

        //the second one
        // create transformations
        transform = glm::mat4(1.0f); // make sure to initialize matrix to identity matrix first
        transform = glm::translate(transform, glm::vec3(-0.5f, 0.5f, 0.0f));
        float scaleAmount = sin((float)glfwGetTime());
        if (scaleAmount < 0)
            transform = glm::scale(transform, glm::vec3(-scaleAmount, -scaleAmount, -scaleAmount));
        else 
            transform = glm::scale(transform, glm::vec3(scaleAmount, scaleAmount, scaleAmount));

        // get matrix's uniform location and set matrix
        ourShader.use();
        glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(transform));

        // render container
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

2019/11/28