engineer-thesis-WUT/Engine/engine/draw.cpp

#ifndef DRAW_CPP
#define DRAW_CPP
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <cmath>
#include "draw.hpp"
#include "renderLoop.hpp"
#include "shaders.hpp"
#include "constants.hpp"
#include "misc.hpp"

int drawFigure(const int whatToDraw)
{
    switch (whatToDraw)
    {
    case 0:
        return drawTriangle(constants::TRIANGLE_VERTICES, constants::TRIANGLE_VERTICES_SIZE, constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE, false);
    case 1:
        return drawSquare(constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE);
    case 2:
        // Try to draw 2 triangles next to each other using glDrawArrays by adding more vertices to your data.
        return drawTriangle(constants::TRIANGLES_VERTICES, constants::TRIANGLES_VERTICES_SIZE, constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE, false);
    case 3:
        // Now create the same 2 triangles using two different VAOs and VBOs for their data
        return (drawTriangle(constants::TRIANGLE_ONE, constants::TRIANGLE_ONE_SIZE, constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE, false) == -1 || drawTriangle(constants::TRIANGLE_TWO, constants::TRIANGLE_TWO_SIZE, constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE, false) == -1);
    case 4:
        // Create two shader programs where the second program uses a different fragment shader that outputs the color yellow; draw both triangles again where one outputs the color yellow
        return (drawTriangle(constants::TRIANGLE_ONE, constants::TRIANGLE_ONE_SIZE, constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE, false) == -1 || drawTriangle(constants::TRIANGLE_TWO, constants::TRIANGLE_TWO_SIZE, constants::VERTEX_SHADER_SOURCE, constants::FRAGMENT_SHADER_SOURCE_YELLOW, false) == -1);
    case 5:
        // Get color from vertex shader to fragment shader
        return drawTriangle(constants::TRIANGLE_VERTICES, constants::TRIANGLE_VERTICES_SIZE, constants::VERTEX_SHADER_COLOR, constants::FRAGMENT_SHADER_COLOR_FROM_VERTEX, false);
    case 6:
        // set color from opengl code to uniform value in fragment shader
        return drawTriangle(constants::TRIANGLE_VERTICES, constants::TRIANGLE_VERTICES_SIZE, constants::VERTEX_SHADER_COLOR, constants::FRAGMENT_SHADER_UNIFORMS, false);
    case constants::MAX_DRAW_CALL:
        // set color from opengl code to uniform value in fragment shader
        return drawTriangle(constants::TRIANGLE_COLORS, constants::TRIANGLE_COLORS_SIZE, constants::VERTEX_SHADER_VERTICE_COLOR, constants::FRAGMENT_SHADER_COLOR_FROM_VERTEX, true);
    default:
        throw "No function for this draw call";
    }
}

int drawSquare(const char* vertexShaderSource, const char* fragmentShaderSource)
{
    const std::pair<unsigned int, unsigned int> shaders = compileShaders(vertexShaderSource, fragmentShaderSource);
    if (shaders.first == 0 || shaders.second == 0)
        return -1;

    const unsigned int shaderProgram = linkShaderObjectsShaderProgram(shaders.first, shaders.second);
    if (shaderProgram == 0)
        return -1;

    const unsigned int VAO = generateBindVAO();
    copyVerticesMemory(constants::SQUARE_VERTICES, constants::SQUARE_VERTICES_SIZE, GL_ARRAY_BUFFER);
    copyVerticesMemory(constants::SQUARE_INDICES, constants::SQUARE_INDICES_SIZE, GL_ELEMENT_ARRAY_BUFFER);

    // set vertex attribute pointers
    configureVertexAttribute(false);

    doDrawElements(shaderProgram, VAO, GL_TRIANGLES, GL_UNSIGNED_INT, std::size(constants::SQUARE_INDICES));
    return 0;
}

void doDrawElements(const unsigned int shaderProgram, const unsigned int vertexArrayObject, const GLenum drawArrayMode, const GLenum drawType, const int numberOfElementsToDraw)
{
    glUseProgram(shaderProgram);
    glBindVertexArray(vertexArrayObject);
    glDrawElements(drawArrayMode, numberOfElementsToDraw, drawType, 0);
    glBindVertexArray(0);
}

int drawTriangle(const float triangleVertices[], const size_t triangleVerticesSize, const char* vertexShaderSource, const char* fragmentShaderSource, const bool colorIncluded)
{
    const unsigned int vertexBufferObject = copyVerticesMemory(triangleVertices, triangleVerticesSize, GL_ARRAY_BUFFER);

    const std::pair<unsigned int, unsigned int> shaders = compileShaders(vertexShaderSource, fragmentShaderSource);
    if (shaders.first == 0 || shaders.second == 0)
        return -1;

    const unsigned int shaderProgram = linkShaderObjectsShaderProgram(shaders.first, shaders.second);
    if (shaderProgram == 0)
        return -1;

    const unsigned int vertexArrayObject = generateBindVAO();
    copyVerticesArray(vertexBufferObject, triangleVertices, triangleVerticesSize, GL_ARRAY_BUFFER);

    // set vertex attribute pointers
    configureVertexAttribute(colorIncluded);
    doDrawArrays(shaderProgram, vertexArrayObject, GL_TRIANGLES, 0, triangleVerticesSize);
    return 0;
}

void updateUniformColor(const unsigned int shaderProgram, const GLchar* uniformName)
{
    // update the uniform color
    const float timeValue = glfwGetTime(); // retrieve running time
    const float greenValue = sin(timeValue) / 2.0f + 0.5f; // vary the color from 0.0 to 1.0 using sin
    const int vertexColorLocation = glGetUniformLocation(shaderProgram, uniformName); // query the location of our uniform
    if(vertexColorLocation != -1)  // if glGetUniformLocation returns -1 it could not find the location 
    { 
        glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f); /* we set the uniform value using glUniform4f
        4f means that it expects 4 floats 
        few of possible postfixes:
            f: the function expects a float as its value.
            i: the function expects an int as its value.
            ui: the function expects an unsigned int as its value.
            3f: the function expects 3 floats as its value.
            fv: the function expects a float vector/array as its value.
        */
    }
}


void doDrawArrays(const unsigned int shaderProgram, const unsigned int vertexArrayObject, const GLenum drawArrayMode, const int firstIndex, const unsigned int numberOfIndicesToBeRendered)
{
    // use shader program to render an object
    glUseProgram(shaderProgram);
    updateUniformColor(shaderProgram, "ourColor");
    glBindVertexArray(vertexArrayObject);
    // From left:
    // primitive type we want to draw
    // starting index of vertex array
    // how many vertices we want to draw
    glDrawArrays(drawArrayMode, firstIndex, numberOfIndicesToBeRendered);
}

#endif