panopainter/engine/shape.cpp

#include "pch.h"
#include "shape.hpp"

bool Shape::create_buffers(GLvoid* idx, GLvoid* vertices, int isize, int vsize)
{
    glGenBuffers(2, buffers);
    if (!(buffers[0] && buffers[1]))
        return false;
    
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffers[1]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, isize, idx, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, buffers[0]);
    glBufferData(GL_ARRAY_BUFFER, vsize, vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    
    glGenVertexArrays(2, arrays);
    if (!(arrays[0] && arrays[1]))
        return false;
    
    for (int i = 0; i < 2; i++)
    {
        glBindVertexArray(arrays[i]);
        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(1);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffers[1]);
        glBindBuffer(GL_ARRAY_BUFFER, buffers[0]);
        glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, sizeof(vertex_t), (GLvoid*)0);
        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(vertex_t), (GLvoid*)offsetof(vertex_t, uvs));
    }
    
    glBindVertexArray(0);
    return true;
}
void Shape::draw_fill() const
{
    glBindVertexArray(arrays[0]);
    glDrawElements(GL_TRIANGLES, count[0], GL_UNSIGNED_SHORT, ioff[0]);
}
void Shape::draw_stroke() const
{
    glBindVertexArray(arrays[1]);
    glDrawElements(GL_LINES, count[1], GL_UNSIGNED_SHORT, ioff[1]);
}

void Plane::create_impl(float w, float h, int div, GLushort *idx, Shape::vertex_t *vertices)
{
    count[0] = div * div * 6;
    count[1] = 8;
    ioff[0] = (GLvoid*)(8 * sizeof(GLushort));
    ioff[1] = (GLvoid*)0;
    
    const float dx = w / div;
    const float dy = h / div;
    const float ox = -w * 0.5f;
    const float oy = -h * 0.5f;
    for (int y = 0; y <= div; y++)
    {
        for (int x = 0; x <= div; x++)
        {
            vertex_t v;
            v.pos.x = ox + dx * (float)x;
            v.pos.y = oy + dy * (float)y;
            v.pos.z = 0;
            v.pos.w = 1;
            v.uvs = glm::vec2(x, y) / (float)div;
            *vertices++ = v;
        }
    }
    
    // generate indices
    *idx++ = 0;                 // A
    *idx++ = (div+1)*(div);     // B
    *idx++ = (div+1)*(div);     // B
    *idx++ = (div+1)*(div+1)-1; // C
    *idx++ = (div+1)*(div+1)-1; // C
    *idx++ = div;               // D
    *idx++ = div;               // D
    *idx++ = 0;                 // A
    for (int y = 0; y < div; y++)
    {
        int i = y * (div+1);
        for (int x = 0; x < div; x++)
        {
            *idx++ = i;
            *idx++ = i + div + 1;
            *idx++ = i + div + 2;
            *idx++ = i;
            *idx++ = i + div + 2;
            *idx++ = i + 1;
            i++;
        }
    }
}

void Circle::create_impl(float radius, int div, GLushort* idx, Shape::vertex_t* vertices)
{
    count[0] = div * 3;
    count[1] = div * 2;
    ioff[0] = (GLvoid*)0;
    ioff[1] = (GLvoid*)(div * 3 * sizeof(GLushort));
    
    auto pidx = idx;
    auto pidx2 = idx + div * 3;
    for (int i = 0; i < div; i++)
    {
        vertex_t v;
        float theta = (float)i / div * M_PI * 2.f;
        glm::vec2 uv = { sinf(theta), cosf(theta) };
        v.pos = glm::vec4(uv * radius, 0, 1);
        v.uvs = uv * 0.5f + 0.5f;
        vertices[i+1] = v;
        
        *pidx++ = 0;
        *pidx++ = i+1;
        *pidx++ = ((i+1) % div) + 1;
        
        *pidx2++ = 1 + i;
        *pidx2++ = 1 + ((i+1) % div);
    }
    vertices[0].pos = { 0, 0, 0, 1 };
    vertices[0].uvs = { 0.5f, 0.5f };
}

void Circle::create_impl(float radius_out, float radius_in, int div, GLushort* idx, Shape::vertex_t* vertices)
{
    count[0] = div * 6;
    count[1] = div * 4;
    ioff[0] = (GLvoid*)0;
    ioff[1] = (GLvoid*)(div * 6 * sizeof(GLushort));
    
    auto pidx = idx;
    auto pidx2 = idx + div * 6;
    for (int i = 0; i < div; i++)
    {
        float theta = (float)i / div * M_PI * 2.f;
        glm::vec2 uv = { sinf(theta), cosf(theta) };
        vertices[i*2].pos = glm::vec4(uv * radius_in, 0, 1);
        vertices[i*2].uvs = uv * (radius_in/radius_out) * 0.5f + 0.5f;
        vertices[i*2+1].pos = glm::vec4(uv * radius_out, 0, 1);
        vertices[i*2+1].uvs = uv * 0.5f + 0.5f;
        
        *pidx++ = i*2;                   // A
        *pidx++ = i*2+1;                 // B
        *pidx++ = ((i+1)*2+1) % (div*2); // C
        
        *pidx++ = i*2;                   // A
        *pidx++ = ((i+1)*2+1) % (div*2); // C
        *pidx++ = ((i+1)*2) % (div*2);   // D
        
        *pidx2++ = i*2;                  // A
        *pidx2++ = ((i+1)*2) % (div*2);  // D

        *pidx2++ = i*2+1;                // B
        *pidx2++ = ((i+1)*2+1) % (div*2);// C
    }
}