/*************************************
*
* Bullet rendering
*
*************************************/
void galaxian_draw_pixel(bitmap_rgb32 bitmap, rectangle cliprect, int y, int x, rgb_t color)
{
if (y >= cliprect.min_y && y <= cliprect.max_y)
{
x *= GALAXIAN_XSCALE;
x += GALAXIAN_H0START;
if (x >= cliprect.min_x && x <= cliprect.max_x)
{
//bitmap.pix32(y, x) = color;
RawBuffer bitmapBuf;
UInt32 bitmapBufOffset = bitmap.pix32(out bitmapBuf, y, x);
bitmapBuf.set_uint32((int)bitmapBufOffset, color);
}
x++;
if (x >= cliprect.min_x && x <= cliprect.max_x)
{
//bitmap.pix32(y, x) = color;
RawBuffer bitmapBuf;
UInt32 bitmapBufOffset = bitmap.pix32(out bitmapBuf, y, x);
bitmapBuf.set_uint32((int)bitmapBufOffset, color);
}
x++;
if (x >= cliprect.min_x && x <= cliprect.max_x)
{
//bitmap.pix32(y, x) = color;
RawBuffer bitmapBuf;
UInt32 bitmapBufOffset = bitmap.pix32(out bitmapBuf, y, x);
bitmapBuf.set_uint32((int)bitmapBufOffset, color);
}
}
}
/*************************************
*
* Draw a row of stars
*
*************************************/
void stars_draw_row(bitmap_rgb32 bitmap, int maxx, int y, UInt32 star_offs, byte starmask)
{
int x;
/* ensure our star offset is valid */
star_offs %= STAR_RNG_PERIOD;
/* iterate over the specified number of 6MHz pixels */
for (x = 0; x < maxx; x++)
{
/* stars are suppressed unless V1 ^ H8 == 1 */
int enable_star = (y ^ (x >> 3)) & 1;
byte star;
/*
* The RNG clock is the master clock (18MHz) ANDed with the pixel clock (6MHz).
* The divide-by-3 circuit that produces the pixel clock generates a square wave
* with a 2/3 duty cycle, so the result of the AND generates a clock like this:
* _ _ _ _ _ _ _ _
* MASTER: _| |_| |_| |_| |_| |_| |_| |_| |
* _______ _______ ______
* PIXEL: _| |___| |___|
* _ _ _ _ _ _
* RNG: _| |_| |_____| |_| |_____| |_| |
*
* Thus for each pixel, there are 3 master clocks and 2 RNG clocks, and the RNG
* is clocked asymmetrically. To simulate this, we expand the horizontal screen
* size by 3 and handle the first RNG clock with one pixel and the second RNG
* clock with two pixels.
*/
/* first RNG clock: one pixel */
star = m_stars[star_offs++];
if (star_offs >= STAR_RNG_PERIOD)
{
star_offs = 0;
}
if (enable_star != 0 && (star & 0x80) != 0 && (star & starmask) != 0)
{
//bitmap.pix32(y, GALAXIAN_XSCALE*x + 0) = m_star_color[star & 0x3f];
RawBuffer bitmapBuf0;
UInt32 bitmapBuf0Offset = bitmap.pix32(out bitmapBuf0, y, GALAXIAN_XSCALE * x + 0);
bitmapBuf0.set_uint32((int)bitmapBuf0Offset, m_star_color[star & 0x3f]);
}
/* second RNG clock: two pixels */
star = m_stars[star_offs++];
if (star_offs >= STAR_RNG_PERIOD)
{
star_offs = 0;
}
if (enable_star != 0 && (star & 0x80) != 0 && (star & starmask) != 0)
{
//bitmap.pix32(y, GALAXIAN_XSCALE*x + 1) = m_star_color[star & 0x3f];
RawBuffer bitmapBuf1;
UInt32 bitmapBuf1Offset = bitmap.pix32(out bitmapBuf1, y, GALAXIAN_XSCALE * x + 1);
bitmapBuf1.set_uint32((int)bitmapBuf1Offset, m_star_color[star & 0x3f]);
//bitmap.pix32(y, GALAXIAN_XSCALE*x + 2) = m_star_color[star & 0x3f];
RawBuffer bitmapBuf2;
UInt32 bitmapBuf2Offset = bitmap.pix32(out bitmapBuf2, y, GALAXIAN_XSCALE * x + 2);
bitmapBuf2.set_uint32((int)bitmapBuf2Offset, m_star_color[star & 0x3f]);
}
}
}
