small3dlib/programs/pokitto/modelViewer.cpp

/*
  Pokitto example demo for small3dlib -- model viewer.

  author: Miloslav Ciz
  license: CC0 1.0
*/

#include "Pokitto.h"

/* Before including small3dlib, we need to define some values for it, such as
  the resolution, the name of the pixel drawing function etc.: */

#define S3L_PIXEL_FUNCTION pixelFunc

#define S3L_RESOLUTION_X 110
#define S3L_RESOLUTION_Y 88

#define S3L_Z_BUFFER 2   // this sets up a reduced precision z-buffer
#define S3L_SORT 0       // no sorting of triangles
#define S3L_STENCIL_BUFFER 0   // no stencil buffer
#define S3L_PERSPECTIVE_CORRECTION 0   /* perspective correction expensive and
                                          dosn't improve quality significantly
                                          with far away models, so turn it off,
                                          but you can try setting it it 2
                                          (approximation) */
#include "small3dlib.h"     // now we can include the library

// include the resources (converted using provided Python scripts):

#include "palette.h"
#include "houseModel.h"
#include "houseTexture.h"
#include "chestModel.h"
#include "chestTexture.h"
#include "earthModel.h"
#include "earthTexture.h"
#include "pokittoModel.h"
#include "pokittoTexture.h"

Pokitto::Core pokitto;

#define MIN_ZOOM (-6 * S3L_FRACTIONS_PER_UNIT)
#define MAX_ZOOM (-16 * S3L_FRACTIONS_PER_UNIT)

#define TEXTURE_W 64
#define TEXTURE_H 64

// helper global variabls and pointers:

int16_t previousTriangle = -1;
S3L_Vec4 uv0, uv1, uv2;
const uint8_t *texture = houseTexture;
const S3L_Index *uvIndices = houseUVIndices;
const S3L_Unit *uvs = houseUVs;

static inline unsigned short sampleTexure(int32_t u, int32_t v)
{
  int index = v * TEXTURE_W + u;

  return texture[index];
}

/* This function will be called by the library to render individual pixels --
   remember, this is the bottleneck, it should be as fast as possible! */
void pixelFunc(S3L_PixelInfo *p)
{
  S3L_Unit u, v;   // texturing coordinates

  if (p->triangleIndex != previousTriangle)
  {
    /* This is a per-triangle cache, it prevents computing per-triangle values
       for each pixel. We only recompute these when the triangleID changes. */

    S3L_getIndexedTriangleValues(p->triangleIndex,uvIndices,uvs,2,&uv0,&uv1,&uv2);
    /* ^ This is a helper funtion that retrieves the 3 UV coordinates of the
       triangle (one for each triangle vertex). */

    previousTriangle = p->triangleIndex;
  }
  
  u = S3L_interpolateBarycentric(uv0.x,uv1.x,uv2.x,p->barycentric);
  v = S3L_interpolateBarycentric(uv0.y,uv1.y,uv2.y,p->barycentric);

  uint8_t c = sampleTexure(u >> 3,v >> 3);
              /* ^ Shifting by 3 gets the value from 0 to 512
                 (S3L_FRACTIONS_PER_UNIT) to 0 to 32 (texture resoltion). */

  // now write the pixel:

  uint8_t *buf = pokitto.display.screenbuffer;

  buf += p->y * S3L_RESOLUTION_X;
  buf += p->x;
  *buf = c;
}

S3L_Scene scene; // our 3D scene, it will only hold one model at a time

void draw()
{
  S3L_newFrame();       // needs to be done before rendering a new frame
  S3L_drawScene(scene); // renders the 3D scene
}

void setModel(uint8_t index)
{
  #define modelCase(n)\
    scene.models = &(n##Model);\
    texture = n##Texture;\
    uvIndices = n##UVIndices;\
    uvs = n##UVs;

  switch (index)
  {
    case 1:
      modelCase(chest)
      break;
    
    case 2:
      modelCase(earth)
      break;

    case 3:
      modelCase(pokitto)
      break;

    default:
      modelCase(house)
      break;
  }

  #undef modelCase
}

uint8_t modelIndex = 0;

int main()
{
  pokitto.begin();

  pokitto.setFrameRate(60);

  pokitto.display.load565Palette(palette);

  houseModelInit();
  chestModelInit();
  earthModelInit();
  pokittoModelInit();

  S3L_initScene(&houseModel,1,&scene);

  setModel(0);

  scene.camera.transform.translation.z = -8 * S3L_FRACTIONS_PER_UNIT;
  // ^ place the camera a little bit to the front so that the model is seen

  while (pokitto.isRunning())
  {
    if (pokitto.update())
    {
      S3L_Unit rotationStep = 8;
      S3L_Unit zoomStep = 128;

      if (pokitto.aBtn())
      {
        if (pokitto.downBtn())
          scene.camera.transform.translation.z =
            S3L_max(MAX_ZOOM,scene.camera.transform.translation.z - zoomStep);
        else if (pokitto.upBtn())
          scene.camera.transform.translation.z =
            S3L_min(MIN_ZOOM,scene.camera.transform.translation.z + zoomStep);
      }
      else
      {
        if (pokitto.upBtn())
          scene.models[0].transform.rotation.x += rotationStep;
        else if (pokitto.downBtn())
          scene.models[0].transform.rotation.x -= rotationStep;
        
        if (pokitto.rightBtn())
          scene.models[0].transform.rotation.y += rotationStep;
        else if (pokitto.leftBtn())
          scene.models[0].transform.rotation.y -= rotationStep;
      }

      if (pokitto.buttons.timeHeld(BTN_B) == 1)
      {
        modelIndex = (modelIndex + 1) % 4;
        setModel(modelIndex);
      }

      draw();
    }
  }
}