2018-soft-3d-renderer/src/loader.cpp

#include "loader.h"
#include <cctype>
#include <cstdio>
#include <cstdint>
#include <cstdlib>
#include <cstring>


// STATIC PROTOTYPES
static char *GetLine(char *buffer, int maxLength, FILE *fp);
static void ComputeNormals(Mesh &mesh);

#pragma pack(push, 1)
struct BMP_Header
{
    uint16_t fileType;
    uint32_t fileSize;
    uint16_t reserved0;
    uint16_t reserved1;
    uint32_t bitmapOffset;
    uint32_t size;
    int32_t width;
    int32_t height;
    uint16_t planes;
    uint16_t bitsPerPixel;
    uint32_t compression;
    uint32_t sizeOfBitmap;
    int32_t horizRes;
    int32_t vertRes;
    uint32_t colorsUsed;
    uint32_t colorsImportant;
};
#pragma pack(pop)


// PUBLIC FUNCTIONS
int LoadMesh(char *filename, Mesh &mesh)
{
    FILE *fp;
    char buffer[256];
    char *token;

    char garbage[5];

    fp = fopen(filename, "r");

    if (fp == NULL)
    {
        fprintf(stderr, "Error loading file: %s\n", filename);
        return -1;
    }

    token = GetLine(buffer, sizeof(buffer), fp);

    while (token != NULL)
    {
        if (token[0] == 'v')
        {
            if (token[1] == ' ')
            {
                Vertex v;

                sscanf(
                        token, "%s %f %f %f",
                        garbage,
                        &v.point.x,
                        &v.point.y,
                        &v.point.z);

                mesh.local.verts.push_back(v);
            }
            else if (token[1] == 't')
            {
                TextureCoord textureCoord;

                sscanf(
                        token, "%s %f %f",
                        garbage,
                        &textureCoord.u,
                        &textureCoord.v);

                mesh.local.uvs.push_back(textureCoord);
            }
        }
        else if (token[0] == 'f')
        {
            Face f;

            sscanf(token, "%s %d/%d %d/%d %d/%d",
                    garbage,
                    &f.vertIndex[0],
                    &f.textureIndex[0],
                    &f.vertIndex[1],
                    &f.textureIndex[1],
                    &f.vertIndex[2],
                    &f.textureIndex[2]);

            // Convert to 0-indexed
            f.vertIndex[0] -= 1;
            f.vertIndex[1] -= 1;
            f.vertIndex[2] -= 1;
            f.textureIndex[0] -= 1;
            f.textureIndex[1] -= 1;
            f.textureIndex[2] -= 1;

            mesh.local.faces.push_back(f);
        }

        token = GetLine(buffer, sizeof(buffer), fp);
    }

    ComputeNormals(mesh);

    printf("Mesh: %s [v: %lu  f: %lu]\n", filename, mesh.local.verts.size(), mesh.local.faces.size());

    mesh.transformed.verts.resize(mesh.local.verts.size());

    fclose(fp);

    return 0;
}

int LoadTexture(char *filename, Texture &texture)
{
    FILE *fp = fopen(filename, "r");
    if (fp == NULL)
    {
        fprintf(stderr, "Could not open file: %s\n", filename);
        return -1;
    }

    BMP_Header header = {};
    fread((void*)&header, sizeof(BMP_Header), 1, fp);
    fseek(fp, header.bitmapOffset, SEEK_SET);

    texture.texels = (ColorU32**)malloc((size_t)header.height * sizeof(ColorU32*));
    for (int row = 0; row < header.height; ++row)
    {
        texture.texels[row] = (ColorU32*)calloc(1, (size_t)header.width * sizeof(ColorU32));
    }

    // Padding is added to image to align to 4-byte boundaries
    size_t paddingSize = header.width % 4;
    uint8_t *padding = (uint8_t*)malloc(paddingSize * sizeof(*padding));

    for (int y = 0; y < header.height; ++y)
    {
        for (int x = 0; x < header.width; ++x)
        {
            fread(&texture.texels[y][x].b, 1, 1, fp);
            fread(&texture.texels[y][x].g, 1, 1, fp);
            fread(&texture.texels[y][x].r, 1, 1, fp);
        }

        // Discard padding byte
        if (paddingSize != 0)
        {
            fread(padding, paddingSize, 1, fp);
        }
    }

    texture.width = (unsigned int)header.width;
    texture.height = (unsigned int)header.height;

    fclose(fp);

    return 0;
}

static char *GetLine(char *buffer, int maxLength, FILE *fp)
{
    while(true)
    {
        if (!fgets(buffer, maxLength, fp))
        {
            return NULL;
        }

        if (buffer[0] != 'v' && buffer[0] != 'f')
        {
            continue;
        }

        return buffer;
    }
}


static void ComputeNormals(Mesh &mesh)
{
    int *vertexNormalCount = (int*)calloc((size_t)(mesh.local.verts.size()), sizeof(int));

    for (size_t f = 0; f < mesh.local.faces.size(); ++f)
    {
        unsigned int v0 = mesh.local.faces[f].vertIndex[0];
        unsigned int v1 = mesh.local.faces[f].vertIndex[1];
        unsigned int v2 = mesh.local.faces[f].vertIndex[2];

        Vector v01 = mesh.local.verts[v1].point - mesh.local.verts[v0].point;
        Vector v02 = mesh.local.verts[v2].point - mesh.local.verts[v0].point;

        Vector normal = Vector::Cross(v01, v02);

        // Add each vertex's normal to the sum for future averaging
        mesh.local.verts[v0].normal += normal;
        mesh.local.verts[v1].normal += normal;
        mesh.local.verts[v2].normal += normal;

        ++vertexNormalCount[v0];
        ++vertexNormalCount[v1];
        ++vertexNormalCount[v2];
    }

    for (size_t v = 0; v < mesh.local.verts.size(); ++v)
    {
        if (vertexNormalCount[v] > 0)
        {
            // Compute the average normal for this vertex
            mesh.local.verts[v].normal /= vertexNormalCount[v];
            mesh.local.verts[v].normal.Normalize();
        }
    }
}