blob: bc61f879cf6221ff66974322e5efe0900e0ebb46 (
plain) (
tree)
|
|
// license:BSD-3-Clause
// copyright-holders:Bryan McPhail, Nicola Salmoria
#include "emu.h"
#include "includes/volfied.h"
/******************************************************
INITIALISATION AND CLEAN-UP
******************************************************/
void volfied_state::video_start()
{
m_video_ram = std::make_unique<uint16_t[]>(0x40000);
m_video_ctrl = 0;
m_video_mask = 0;
save_pointer(NAME(m_video_ram.get()), 0x40000);
save_item(NAME(m_video_ctrl));
save_item(NAME(m_video_mask));
}
/*******************************************************
READ AND WRITE HANDLERS
*******************************************************/
READ16_MEMBER(volfied_state::video_ram_r)
{
return m_video_ram[offset];
}
WRITE16_MEMBER(volfied_state::video_ram_w)
{
mem_mask &= m_video_mask;
COMBINE_DATA(&m_video_ram[offset]);
}
WRITE16_MEMBER(volfied_state::video_ctrl_w)
{
COMBINE_DATA(&m_video_ctrl);
}
READ16_MEMBER(volfied_state::video_ctrl_r)
{
/* Could this be some kind of hardware collision detection? If bit 6 is
set the game will check for collisions with the large enemy, whereas
bit 5 does the same for small enemies. Bit 7 is also used although
its purpose is unclear. This register is usually read during a VBI
and stored in work RAM for later use. */
return 0x60;
}
WRITE16_MEMBER(volfied_state::video_mask_w)
{
COMBINE_DATA(&m_video_mask);
}
WRITE16_MEMBER(volfied_state::sprite_ctrl_w)
{
m_pc090oj->set_sprite_ctrl((data & 0x3c) >> 2);
}
/*******************************************************
SCREEN REFRESH
*******************************************************/
void volfied_state::refresh_pixel_layer( bitmap_ind16 &bitmap )
{
/*********************************************************
VIDEO RAM has 2 screens x 256 rows x 512 columns x 16 bits
x--------------- select image
-x-------------- ? (used for 3-D corners)
--x------------- ? (used for 3-D walls)
---xxxx--------- image B
-------xxx------ palette index bits #8 to #A
----------x----- ?
-----------x---- ?
------------xxxx image A
'3d' corners & walls are made using unknown bits for each
line the player draws. However, on the pcb they just
appear as solid black. Perhaps it was prototype code that
was turned off at some stage.
*********************************************************/
uint16_t* p = m_video_ram.get();
int width = m_screen->width();
int height = m_screen->height();
if (m_video_ctrl & 1)
p += 0x20000;
for (int y = 0; y < height; y++)
{
for (int x = 1; x < width + 1; x++) // Hmm, 1 pixel offset is needed to align properly with sprites
{
int color = (p[x] << 2) & 0x700;
if (p[x] & 0x8000)
{
color |= 0x800 | ((p[x] >> 9) & 0xf);
if (p[x] & 0x2000)
color &= ~0xf; /* hack */
}
else
color |= p[x] & 0xf;
bitmap.pix16(y, x - 1) = color;
}
p += 512;
}
}
uint32_t volfied_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
{
screen.priority().fill(0, cliprect);
refresh_pixel_layer(bitmap);
m_pc090oj->draw_sprites(bitmap, cliprect, screen.priority(), 0);
return 0;
}
|