70 lines
1.9 KiB
C++
70 lines
1.9 KiB
C++
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#include "widget.hpp"
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#include "gfx.hpp"
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#include <glm/gtc/matrix_transform.hpp>
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#include <GLFW/glfw3.h>
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Widget::Widget(Orbit& orbit, GLuint shaderProgram) :
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_orbit(orbit),
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_shaderProgram(shaderProgram)
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{
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const float lineLength = 0.1;
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for (int i = 0; i < 3*6; i++)
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{
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_vertices[i] *= _lineLength;
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}
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glGenVertexArrays(1, &_vao);
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glGenBuffers(1, &_vbo);
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glBindVertexArray(_vao);
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glBindBuffer(GL_ARRAY_BUFFER, _vbo);
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size_t v3Size = 3 * sizeof(float);
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size_t lineSize = 2 * sizeof(float);
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size_t vboBufferSize = v3Size * lineSize * 3;
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glBufferData(GL_ARRAY_BUFFER, vboBufferSize, &_vertices[0], GL_STATIC_DRAW);
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glEnableVertexAttribArray(0);
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glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
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glBindBuffer(GL_ARRAY_BUFFER, 0);
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glBindVertexArray(0);
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}
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void Widget::render()
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{
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updateModelMatrix();
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glBindVertexArray(_vao);
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glBindBuffer(GL_ARRAY_BUFFER, _vbo);
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glDrawArrays(GL_LINES, 0, 6);
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}
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void Widget::updateModelMatrix()
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{
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float p = glfwGetTime();
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_position = _orbit.getPosition(p);
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// get the tangent of the orbital ellipse
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glm::vec3 tan = _orbit.getTangent(p);
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// we want to point along the orbit
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glm::vec3 target = _position + tan;
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// 'up' is just the normalized position vector because the orbit is centred at the origin
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glm::vec3 up = glm::normalize(_position);
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// easy peasy lookAt matrix
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glm::mat4 look = glm::lookAt(_position, target, up);
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// invert the lookat matrix because it's meant for cameras, cameras work backwards and
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// we are not a camera
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glm::mat4 model = glm::inverse(look);
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GLint modelLocation = getShaderUniformLocation(_shaderProgram, "_Model");
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glUniformMatrix4fv(modelLocation, 1, GL_FALSE, &model[0][0]);
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}
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Widget::~Widget()
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{
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glDeleteVertexArrays(1, &_vao);
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glDeleteBuffers(1, &_vbo);
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}
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