// license:BSD-3-Clause // copyright-holders:Luca Elia /*************************************************************************** -= Sky Fox / Exerizer =- driver by Luca Elia (l.elia@tin.it) [ 1 Background ] The stars in the background are not tile based (I think!) and their rendering is entirely guesswork for now.. I draw a star for each horizontal line using 2 bytes in the background rom: - the first byte seems a color / shape info - the second byte seems a position info The rom holds 4 chunks of $2000 bytes. Most of the data does not change between chunks, while the remaining part (which is rendered to what seems a "milky way") pulsates in color and/or shape to simulate the shimmering of stars (?!) if we draw one chunk only and cycle through the four. Indeed, there's a register cycling through 4 values. Since the result kind of matches a screenshot we have, I feel the drawn result is not that far from reality. On the other hand we have a random arrangement of stars, so it's hard to tell for sure.. [ 256 Sprites ] Sprites are 8 planes deep and can be 8x8, 16x16 or 32x32 pixels in size. They are stored as 32x32x8 tiles in the ROMs. ***************************************************************************/ #include "emu.h" #include "video/resnet.h" #include "includes/skyfox.h" /*************************************************************************** Convert the color PROMs into a more useable format. There are three 256x4 palette PROMs (one per gun). The palette PROMs are connected to the RGB output this way: bit 3 -- 110 ohm resistor -- RED/GREEN/BLUE -- 220 ohm resistor -- RED/GREEN/BLUE -- 680 ohm resistor -- RED/GREEN/BLUE bit 0 -- 1.2kohm resistor -- RED/GREEN/BLUE ***************************************************************************/ static const res_net_decode_info skyfox_decode_info = { 1, 0, 255, // start/end // R, G, B, { 0, 0x100, 0x200, }, // offsets { 0, 0, 0, }, // shifts { 0xf, 0xf, 0xf, } // masks }; static const res_net_info skyfox_net_info = { RES_NET_VCC_5V | RES_NET_VBIAS_5V | RES_NET_VIN_TTL_OUT, { { RES_NET_AMP_NONE, 0, 0, 4, { 1200, 680, 220, 110 } }, { RES_NET_AMP_NONE, 0, 0, 4, { 1200, 680, 220, 110 } }, { RES_NET_AMP_NONE, 0, 0, 4, { 1200, 680, 220, 110 } } } }; PALETTE_INIT_MEMBER(skyfox_state, skyfox) { const uint8_t *color_prom = memregion("proms")->base(); std::vector rgb; compute_res_net_all(rgb, color_prom, skyfox_decode_info, skyfox_net_info); palette.set_pen_colors(0, rgb); /* Grey scale for the background??? is wrong */ for (int i = 0; i < 256; i++) { palette.set_pen_color(i + 256, rgb_t(i, i, i)); } } /*************************************************************************** Sprites Drawing Offset: Value: 03 Code: selects one of the 32x32 tiles in the ROMs. (Tiles $80-ff are bankswitched to cover $180 tiles) 02 Code + Attr 7654 ---- Code (low 4 bits) 8x8 sprites use bits 7654 (since there are 16 8x8 tiles in the 32x32 one) 16x16 sprites use bits --54 (since there are 4 16x16 tiles in the 32x32 one) 32x32 sprites use no bits (since the 32x32 tile is already selected) 7--- 3--- Size 1--- 1--- : 32x32 sprites 0--- 1--- : 16x16 sprites 8x8 sprites otherwise ---- -2-- Flip Y ---- --1- Flip X ---- ---0 X Low Bit 00 Y 01 X (High 8 Bits) ***************************************************************************/ void skyfox_state::draw_sprites( bitmap_ind16 &bitmap, const rectangle &cliprect ) { gfx_element *gfx = m_gfxdecode->gfx(0); int width = m_screen->width(); int height = m_screen->height(); /* The 32x32 tiles in the 80-ff range are bankswitched */ int shift = (m_bg_ctrl & 0x80) ? (4 - 1) : 4; for (int offs = 0; offs < m_spriteram.bytes(); offs += 4) { int xstart, ystart, xend, yend; int xinc, yinc, dx, dy; int low_code, high_code, n; int code = m_spriteram[offs + 3] << 8 | m_spriteram[offs + 2]; int flipx = code & 0x2; int flipy = code & 0x4; int y = m_spriteram[offs + 0]; int x = m_spriteram[offs + 1] << 1 | (code & 1); high_code = ((code >> 4) & 0x7f0) + ((code & 0x8000) >> shift); switch (code & 0x88) { case 0x88: n = 4; low_code = 0; break; case 0x08: n = 2; low_code = (code & 0x20) >> 2 | (code & 0x10) >> 3; break; default: n = 1; low_code = (code >> 4) & 0xf; break; } if (m_bg_ctrl & 1) // flipscreen { x = width - x - (n - 1) * 8; y = height - y - (n - 1) * 8; flipx = !flipx; flipy = !flipy; } if (flipx) { xstart = n - 1; xend = -1; xinc = -1; } else { xstart = 0; xend = n; xinc = +1; } if (flipy) { ystart = n - 1; yend = -1; yinc = -1; } else { ystart = 0; yend = n; yinc = +1; } code = low_code + high_code; for (dy = ystart; dy != yend; dy += yinc) { for (dx = xstart; dx != xend; dx += xinc, code++) { gfx->transpen(bitmap, cliprect, code, 0, flipx, flipy, dx*8 + x, dy*8 + y, 0xff); // wraparound y - BTANB: large sprites exiting the screen sometimes reappear on the other edge gfx->transpen(bitmap, cliprect, code, 0, flipx, flipy, dx*8 + x, dy*8 + y - 256, 0xff); } if (n == 2) code += 2; } } } /*************************************************************************** Background Rendering ***************************************************************************/ void skyfox_state::draw_background(bitmap_ind16 &bitmap, const rectangle &cliprect) { uint8_t *rom = memregion("gfx2")->base(); /* The foreground stars (sprites) move at twice this speed when the bg scroll rate [e.g. (m_bg_ctrl >> 1) & 7] is 4 */ int pos = (m_bg_pos >> 4) & (512 * 2 - 1); for (int i = 0; i < 0x1000; i++) { int offs = (i * 2 + ((m_bg_ctrl >> 4) & 0x3) * 0x2000) % 0x8000; int pen = rom[offs]; int x = rom[offs + 1] * 2 + (i & 1) + pos + ((i & 8) ? 512 : 0); int y = ((i / 8) / 2) * 8 + (i % 8); if (m_bg_ctrl & 1) // flipscreen { x = 512 * 2 - (x % (512 * 2)); y = 256 - (y % 256); } for (int j = 0; j <= ((pen & 0x80) ? 0 : 3); j++) bitmap.pix16((((j / 2) & 1) + y) % 256, ((j & 1) + x) % 512) = 256 + (pen & 0x7f); } } /*************************************************************************** Screen Drawing ***************************************************************************/ uint32_t skyfox_state::screen_update_skyfox(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect) { bitmap.fill(0xff, cliprect); // the bg is black draw_background(bitmap, cliprect); draw_sprites(bitmap, cliprect); return 0; }