sy2002
commented
3 years ago @MJoergen Great job! I could not resist to quickly trying your latest commit in branch dev-vga-fractional on real hardware: As you wrote in your email, the whole thing was a bit slow and jerky. But then I removed the line that syncs with the 60 Hz of the screen:
//while ((y = MMIO(VGA_SCAN_LINE)) >= 480)And then everything starts to look totally smooth and pretty. I made a small video. Download, unpack and look at this:
Now it is a bit too fast.
The solution: I think what we (reads "you?" :-)) might want to add to the monitor (misc library) and then also via qmon.h to C is a simple and synchroneous delay function in microseconds.
Simple and synchroneous means that we do not need the timer interrupt for that. Since we have switched on the cycle-counter be default, it is as easy as counting some cycles (and making sure that we cover wrap arounds). The counters are 48bit or so, so that wrap arounds would only happen every ~65 days if I calculated correctly ;-)
And then we could do a qmon_delay(100000) (which is 0,1 seconds in microseconds) as the function would be defined like qmon_delay(unsigned long microseconds) and then all would be good?
P.S. As your new fractional pixel scaling is not breaking anything, you might want to get rid of the branch and put everything in develop?
MJoergen
This issue is about enabling fractional scaling of the display. The idea is to allow easy implementation of almost-3D games like Wolfenstein or to make smooth 3D text scrolling like in the Star Wars intro! This is for you @sy2002 !!
The idea is to add two new registers that contain the ratio of the pixel width in the screen buffer versus the pixel width on the monitor display, i.e.
Each register value contains the size of a screen buffer pixel in units of monitor display pixels, scaled by a constant value of 256. So the default value is
0x0100, corresponding to a scaling factor of 1. The value0x0080would mean only half the screen buffer is used to fill the entire monitor display. In other words, this leads to a magnification by a factor of 2.The implementation could be as easy as expanding the module
vga_pixel_countersand adding another set of pixel counter outputs. So one set gives the coordinates on the monitor display (and counts by 1 every clock cycle), and the other set gives the coordinates on the screen buffer (and counts byVGA_PIXEL_X_SCALE/256every clock cycle). The outputs could be calledmonitor_pixel_*andbuffer_pixel_*, respectively. Then themonitor_pixel_*signals are fed into thevga_syncmodule, while thebuffer_pixel_*signals are fed intovga_text_modeandvga_spriteetc.This issue includes writing a cool demo!