One of the (many) limitations of MIDP 1.0 is that it lacks the fillTriangle that is present in MIDP 2.0. Below is a replacement method that works on MIDP 1.0 devices. It is based on notes published by Michal Wronski.

Michal’s algorithm depends on floating-point math – also unavailable in MIDP 1.0. With a little refactoring I was able to create an integer-only approximation. Sadly, rounding errors mean that my routine isn’t pixel perfect. An alternative that would give more accurate results would be to use some kind of fixed-point library. Despite its shortcomings, however, my method is good enough for many practical purposes (including my own).

[sourcecode language='java'] protected void drawHorizontalLine(int x1, int x2, int y) { graphics.drawLine(x1, y, x2, y); } protected void fillTriangle(int ax, int ay, int bx, int by, int cx, int cy) { // http://www.geocities.com/wronski12/3d_tutor/tri_fillers.html // Sort the points so that ay <= by <= cy. if (ay > by) { temp = ax; ax = bx; bx = temp; temp = ay; ay = by; by = temp; } if (by > cy) { temp = bx; bx = cx; cx = temp; temp = by; by = cy; cy = temp; } if (ay > by) { temp = ax; ax = bx; bx = temp; temp = ay; ay = by; by = temp; } // Calc the deltas for each edge. int ab_num; int ab_den; if (by - ay > 0) { ab_num = (bx - ax); ab_den = (by - ay); } else { ab_num = (bx - ax); ab_den = 1; } int ac_num; int ac_den; if (cy - ay > 0) { ac_num = (cx - ax); ac_den = (cy - ay); } else { ac_num = 0; ac_den = 1; } int bc_num; int bc_den; if (cy - by > 0) { bc_num = (cx - bx); bc_den = (cy - by); } else { bc_num = 0; bc_den = 1; } // The start and end of each line. int sx; int ex; // The heights of the two components of the triangle. int h1 = by - ay; int h2 = cy - by; // If a is to the left of b... if (ax < bx) { // For each row of the top component... for (int y = 0; y < h1; y++) { sx = ax + ac_num * y / ac_den; ex = ax + ab_num * y / ab_den; drawHorizontalLine(sx, ex, ay + y); } // For each row of the bottom component... for (int y = 0; y < h2; y++) { int y2 = h1 + y; sx = ax + ac_num * y2 / ac_den; ex = bx + bc_num * y / bc_den; drawHorizontalLine(sx, ex, by + y); } } else { // For each row of the bottom component... for (int y = 0; y < h1; y++) { sx = ax + ab_num * y / ab_den; ex = ax + ac_num * y / ac_den; drawHorizontalLine(sx, ex, ay + y); } // For each row of the bottom component... for (int y = 0; y < h2; y++) { int y2 = h1 + y; sx = bx + bc_num * y / bc_den; ex = ax + ac_num * y2 / ac_den; drawHorizontalLine(sx, ex, by + y); } } } [/sourcecode]

I release this code into the public domain. You can use it as you please.

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