sprite.cpp

#include <iostream>
#include <string>
#include <glm/gtc/type_ptr.hpp>

#include "sprite.h"

namespace game {

Sprite::Sprite(void) : Geometry()
{
    // Initialize variables with default values
    vbo_ = 0;
    ebo_ = 0;
    size_ = 0;
}


void Sprite::CreateGeometry(void){

    // The face of the square is defined by four vertices and two triangles

    // Number of attributes for vertices and faces
    // const int vertex_att = 7;  // 7 attributes per vertex: 2D (or 3D) position (2), RGB color (3), 2D texture coordinates (2)
    // const int face_att = 3; // Vertex indices (3)

    GLfloat vertex[]  = {
        // Four vertices of a square
        // Position      Color                Texture coordinates
        -0.5f,  0.5f,    1.0f, 0.0f, 0.0f,    0.0f, 0.0f, // Top-left
         0.5f,  0.5f,    0.0f, 1.0f, 0.0f,    1.0f, 0.0f, // Top-right
         0.5f, -0.5f,    0.0f, 0.0f, 1.0f,    1.0f, 1.0f, // Bottom-right
        -0.5f, -0.5f,    1.0f, 1.0f, 1.0f,    0.0f, 1.0f  // Bottom-left
    };

    // Two triangles referencing the vertices
    GLuint face[] = {
        0, 1, 2, // t1
        2, 3, 0  // t2
    };

    // Create buffer for vertices
    glGenBuffers(1, &vbo_);
    glBindBuffer(GL_ARRAY_BUFFER, vbo_);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW);

    // Create buffer for faces (index buffer)
    glGenBuffers(1, &ebo_);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo_);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(face), face, GL_STATIC_DRAW);

    // Set number of elements in array buffer (6 in this case)
    size_ = sizeof(face) / sizeof(GLuint);
}


void Sprite::SetGeometry(GLuint shader_program)
{

    // No blending
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    glDisable(GL_BLEND);

    // Bind buffers
    glBindBuffer(GL_ARRAY_BUFFER, vbo_);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo_);

    // Set attributes for shaders
    // Should be consistent with how we created the buffers for the square
    GLint vertex_att = glGetAttribLocation(shader_program, "vertex");
    glVertexAttribPointer(vertex_att, 2, GL_FLOAT, GL_FALSE, 7 * sizeof(GLfloat), 0);
    glEnableVertexAttribArray(vertex_att);

    GLint color_att = glGetAttribLocation(shader_program, "color");
    glVertexAttribPointer(color_att, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(GLfloat), (void *)(2 * sizeof(GLfloat)));
    glEnableVertexAttribArray(color_att);

    GLint tex_att = glGetAttribLocation(shader_program, "uv");
    glVertexAttribPointer(tex_att, 2, GL_FLOAT, GL_FALSE, 7 * sizeof(GLfloat), (void *)(5 * sizeof(GLfloat)));
    glEnableVertexAttribArray(tex_att);
}

} // namespace game