| Code: |
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glBegin(GL_TRIANGLES); glVertex3f( 0.0f, 1.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f); glEnd(); |
| Code: |
| fill_poly (point1, point2, point3)
{ draw_line (point1, point2, min_max); draw_line (point2, point3, min_max); draw_line (point3, point1, min_max); interpolate(min_max); } draw_line (a, b, min_max) { foreach (pixel p in a->b) { put_pixel (p); min_max[p.y].min = MIN (p.x, min_max.min[p.y]); min_max[p.y].max = MAX (p.x, min_max.max[p.y]); } } interpolate (min_max) { for (y = 0; y < min_max.max_y(); ++y) { for (x = min_max[y].min; x < min_max[y].max; ++x) put_pixel (x,y); } } |
| keldon wrote: | ||
| The scanline method is about the easiest to code; you can even store uv and uz deltas for texture mapping without too much effort.
Just to show you in code:
And just as mike said, you can store what you want at the beginning and end of the line. In the interpolate method you might read that RED is the colour on the left and BLUE is the colour on the right, and write a gradient using the interpolated values. As a matter of fact, I've used it a few times myself. p.s. I didn't implement it using those methods exactly, I'm just trying to show you the general logic. |
| hacker013 wrote: |
| can you give an working example because it is for me to complicated. |
| hacker013 wrote: |
| can you give an working example because it is for me to complicated. |
| Code: |
| /*!
Draws a texture mapped polygon to img. \param img Destination image \param points KPoint*[npoints] \param npoints Number of points in 'points' parameter. */ void drawPoly (wxImage *img, const KPoint **points, int npoints) { int minx [img->getHeight()]; int maxx [img->getHeight()]; int miny = img->getHeight(); int maxy = 0; // > // Initialize min/max in such a way that nothing will be drawn for each line // > for ( int i = 0; i < img->getHeight(); i ++ ) { minx[i] = img->getWidth(); maxx[i] = 0; } // > // Calculate minx and maxx for each line, aswell as miny and maxy // > for ( int i = 0; i < npoints -1; i ++ ) { KPoint *p1 = points[i]; KPoint *p2 = points[i+1]; KEdge e( p1, p2); // > // KEdge stores some calculations on an edge designed to draw // an edge line by line. In short, each point in the line will be // reached. // > for ( int dx = e.a->x <<16, dy = e.a->y <<16, cy = 0; cy < e.diffy ; cy++ ) { int x = dx >> 16; int y = dy >> 16; if ( x < minx[y]) { minx[y] = x; } if ( x > maxx[y]) maxx[y] = x; if ( y < miny ) miny = y; if ( y > maxy ) maxy = y; dx += e.dx; dy += e.dy; } } // > // Render shape using min/max values created when drawing the lines. // > for ( int y = miny; y <= maxy; y ++ ) { for ( int x = minx[y]; x <= maxx[y]; x++ ) { img->SetRGB(x,y, WHITE); } } } |
| Code: |
| #define MIN( a, b ) ( (a)<(b)?(a):(b) )
#define MAX( a, b ) ( (a)>(b)?(a):(b) ) #define ABS( a ) ( (a)<0?-(a):(a) ) #define FABS( a ) ( (a)<0.0?-(a):(a) ) #define LIMIT( v, min, max ) ( (v)>(max)?(max):((v)<(min)?(min):v) ) #define IN_RANGE( val, MIN, MAX ) ( ( MIN <= val && MAX >= val ) ? 1 : 0 ) #define OUT_OF_RANGE( val, MIN, MAX ) ( ( MIN <= val && MAX >= val ) ? 0 : ( ( MIN > val ) ? -1 : 1 ) ) class IMAGE; typedef u16 COLOUR; /*! \class IMAGE \brief This is the interface used in drawPoly. */ class IMAGE { public: void set_pixel (int x, int y, COLOUR colour); u32 get_width (void) const; u32 get_height (void) const; }; class SCANLINE_BOUNDARY { public: SCANLINE_BOUNDARY (u32 *minx, u32 *maxx, u32 height) : minx_ (minx), maxx_ (maxx), height_ (height) {} void set_pixel (int x, int y, COLOUR) { if (minx_ && maxx_ && (y >= 0) && (y < height_)) { minx_[y] = MIN (minx_[y], x); maxx_[y] = MAX (maxx_[y], x); } } private: u32 height_; u32 *minx_; u32 *maxx_; }; class POINT { public: int get_x() {return 1;} int get_y() { return 1;} }; void drawPoly (IMAGE &img, const POINT &p1, const POINT &p2, const POINT &p3, COLOUR colour); template <class T> void draw_line(T &image, POINT p1, POINT p2, COLOUR color); /*! Draws a texture mapped polygon to img. \param img Destination image \param points KPoint*[npoints] \param npoints Number of points in 'points' parameter. */ void drawPoly (IMAGE &img, const POINT &p1, const POINT &p2, const POINT &p3, COLOUR colour) { // minx and maxx could be changed to dynamically allocated arrays, but // I opted for stack allocated arrays. const int MAX_IMAGE_HEIGHT = 512; u32 minx [MAX_IMAGE_HEIGHT]; u32 maxx [MAX_IMAGE_HEIGHT]; u32 miny = img.get_height(); u32 maxy = 0; // > // Initialize min/max in such a way that nothing will be drawn for each line // > for ( int i = 0; i < img.get_height(); i ++ ) { minx[i] = img.get_width(); maxx[i] = 0; } SCANLINE_BOUNDARY boundary (minx, maxx, img.get_height()); draw_line(boundary, p1, p2, colour); draw_line (boundary, p2, p3, colour); draw_line (boundary, p3, p1, colour); // > // Render shape using min/max values created when drawing the lines. // > for ( u32 y = miny; y <= maxy; y ++ ) { for ( u32 x = minx[y]; x <= maxx[y]; x++ ) { img.set_pixel((int)x,(int)y, colour); } } } template <class T> void draw_line(T &image, POINT p1, POINT p2, COLOUR color) { int x = p1.get_x(); int y = p1.get_y(); int x2 = p2.get_x(); int y2 = p2.get_y(); int w = x2 - x ; int h = y2 - y ; int dx1 = 0, dy1 = 0, dx2 = 0, dy2 = 0 ; if (w<0) dx1 = -1 ; else if (w>0) dx1 = 1 ; if (h<0) dy1 = -1 ; else if (h>0) dy1 = 1 ; if (w<0) dx2 = -1 ; else if (w>0) dx2 = 1 ; int longest = ABS(w) ; int shortest = ABS(h) ; if (!(longest>shortest)) { longest = ABS(h) ; shortest = ABS(w) ; if (h<0) dy2 = -1 ; else if (h>0) dy2 = 1 ; dx2 = 0 ; } int numerator = longest >> 1 ; for (int i=0;i<=longest;i++) { image.set_pixel(x,y,color) ; numerator += shortest ; if (!(numerator<longest)) { numerator -= longest ; x += dx1 ; y += dy1 ; } else { x += dx2 ; y += dy2 ; } } } |