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First post, by digistorm

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Since the new vgaonly mode with the scanline precision and all, the colors are no longer correct on my system. At least, I guess it is since version 0.74 because I have done a lot of capturing in the vgaonly mode and only recently I stumbled upon this error.

What happens in WINDOWED mode is: the red color channel is mapped to the green one, the green color channel is mapped to the red one, and the blue color channel remains black. So red is green, green is red, white is yellow (because of the lack of blue).
What happens in FULL SCREEN mode is: the blue color channel seems normal, but the red and green channel reach maximum brightness at half the range and then starts again. So when a single red or green gradient is displayed, it renders two gradients next to each other. It looks like if the red and green channel registers/variables are bit-shifted or rotated, or something like that.

I have added a screenshot of the demo Unreal (1992) at the point where it shows the three primary colors mixing in circular gradients. It is large but it shows the error pretty well.

My machine is an Intel Mac, Core 2 Duo, with Snow Leopard (10.6.4) installed. The videochip inside is a Radeon X1600 but has never given problems before. I hope you have use of this error report 😀

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    vgaonly_render_error.png
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Reply 2 of 8, by Qbix

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problem is with the macs only. sdl has a different pixel ordering from what we expect. (as we write directly into the pixel buffer)

Water flows down the stream
How to ask questions the smart way!

Reply 3 of 8, by digistorm

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I see I have probably used a different profile, because demo's that require svga normally also require more cpu power and vice versa. But the problem does not seem to be cpu related. I can post my configuration files if that helps, but I don't know exactly which ones because I use Dapplegray, a launcher, to switch configurations.

Reply 4 of 8, by digistorm

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Is it possible for the devs to look into this problem of SDL? Or is it a problem of the SDL library and is there nothing the dev team can do?
I ask this because 0.73 did not have this problem, except for hi-color fullscreen modes. 256 color works perfect fullscreen and all modes work correct in windowed mode. So I switched back to 0.73 because 0.74 is not usable on my Mac (and so it seems, on any Mac?).
If it is the fault of the SDL lib, is there something else that can be done or that explains why it "almost" works in 0.73 and not at all in 0.74?
I really like the new features in the 0.74 version so I would be glad to switch back.

Reply 5 of 8, by IIGS_User

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digistorm wrote:

II can post my configuration files if that helps, but I don't know exactly which ones because I use Dapplegray, a launcher, to switch configurations.

Please use Dapplegrey's menu 'DOSBox' to 'View Config file' to see its content.

Plus, when you start the game, the config file will be written to the folder
"~/users/yourname/Library/Application Support/Dapplegrey/Unreal"

The "Unreal" word in the path may vary, please check Dapplegrey's 'Game Files' tab panel, at 'Save Captures to:' ("Open In Finder").

Klimawandel.

Reply 6 of 8, by dvwjr

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Well, this is not Apple MAC (Intel) related, but it is DOSBox v0.74 "machine=vgaonly" relevant.

System:
-------------------------------------------------
Microsoft Windows 98 4.10.2222 A

AOpen AX6BC (Intel 440BX) (BIOS v2.59)
Intel 1400MHz (Tualatin) via PowerLeap adapter
GenuineIntel x86 Family 6 Model 8 Stepping 10
755MB RAM


Video Adapter:
-------------------------------------------------------
NVIDIA GeForce FX 5950 Ultra (AGP 2x, 256MB RAM)
NVIDIA vBIOS version 4.35.20.32.16
NVIDIA driver version 82.69
Microsoft DirectX 9.0c [i](updated through Dec 13, 2006)[/i]



Video Test Programs:
------------------------------------------------
DisplayMate for Windows version 1.2
DisplayMate Professional for DOS version 1.2

Test Pattern: 64 intensities for Primary Colors (Color ramp - 2:21)
Test Resolution: VGA 320 x 200 pixels (mode 0x13)

DOS TSR screen capture program: PCXDump v9.32
Windows image viewer/resizer: IrfanView v4.27

Noticed a color display problem with DOSBox v0.74 on a Win98/nVidia PC with the "machine=vgaonly" setting. This color display problem does not occur with DOSBox v0.74 and the "machine=svga_s3" setting. The error which occurs with "machine=vgaonly" is not influenced by how the [sdl] output setting is configured (ie, surface, overlay, opengl, openglnb, ddraw).

The DisplayMate (SONERA) Technologies video test programs DisplayMate for Windows and DisplayMate Professional for DOS were used to display a 64 intensities Gray-scale and RGB color ramp on the PC platform described above.

First, the Windows version of DisplayMate was used to display the color ramp test pattern on a 640x400 Desktop to check the nVidia Windows video drivers (v82.69) color display output on the nVidia FX-5950 Ultra, when a full-screen test pattern was captured. This can be seen in the attached file: DisplayMateWindows_64scale.png

Second, the DOS version of DisplayMate was used to display the same color ramp test pattern under DOS 7.1 from the nVidia FX-5950 Ultra VGA adapter, using the screen capture program PCXdump v9.32 for the test pattern displayed in VGA mode 0x13 (320 x 200 x 256 colors). The native 320x200 PCX capture file was re-sized to 640x400 when converted to the PNG format. This can be seen in the attached file: nVidia_5950U_VGA_DMP_64scale_resized_PCXDUMP.png

Third, the DOS version of DisplayMate was used to display the same color ramp test pattern under DOSBox v0.74 using the "machine=svga_s3" setting, which was captured using the native DOSBox CTRL-F5 screen capture mechanism for the test pattern displayed in VGA mode 0x13 (320 x 200 x 256 colors). The native 320x200 PNG file was re-sized to 640x400 when saved as the PNG format. This can be seen in the attached file: DosBox_074_svga_S3_DMP_64scale.png

Fourth, the DOS version of DisplayMate was used to display the same color ramp test pattern under DOSBox v0.74 using the "machine=vgaonly" setting, which was captured using the native DOSBox CTRL-F5 screen capture mechanism for the test pattern displayed in VGA mode 0x13 (320 x 200 x 256 colors). The native 640x400 screen capture file was saved in the DOSBox native PNG format. This file is the one which displays the the color and intensity problems of the "machine=vgaonly" setting of DOSBox v0.74. This can be seen in the attached file: DosBox_074_VGAonly_DMP_64scale.png

Fifth, the DOS version of DisplayMate was used to display the same color ramp test pattern under DOSBox v0.74 using the "machine=vgaonly" setting, which was captured using the screen capture TSR PCXdump v9.32 screen capture mechanism for the test pattern displayed in VGA mode 0x13 (320 x 200 x 256 colors). The PCXdump v9.32 TSR was used instead of the native DOSBox v0.74 CTRL-F5 screen capture method to see if the image captured from the emulated VGA frame buffer was actually correct. The video data captured from the DOSBox VGA frame buffer appears to be correct as captured by the PCXdump v9.32 TSR. This can be seen in the attached file: DosBox_074_VGAonly_DMP_64scale_PCXDUMP.png

Examination of the file DosBox_074_VGAonly_DMP_64scale.png shows that only the Green 64 intensity ramp appears to be displayed properly. The Red and Blue color ramps only appear to display 32 different color intensities as compared to the 64 Green intensities. Most apparent is the 64 intensity Gray-scale, which is not any longer a Gray-scale, as visible amounts of Red and perhaps Green can be seen instead of a smoothly progressive Gray-scale.

Contrast this above mentioned image with the comparison file DosBox_074_VGAonly_DMP_64scale_PCXDUMP.png which was captured with the PCXdump v9.32 TSR from the same DOSBox "machine=vgaonly" v0.74 session. This image captured via the PCXdump TSR appears to be correct, while the DOSBox v0.74 display and native CTRL-F5 screen capture output appear to be corrupt.

Perhaps I am just missing something obvious... 😳

Attached files:
----------------------------------------------------
1.) DisplayMateWindows_64scale.png
2.) nVidia_5950U_VGA_DMP_64scale_resized_PCXDUMP.png
3.) DosBox_074_svga_S3_DMP_64scale.png
4.) DosBox_074_VGAonly_DMP_64scale.png
5.) DosBox_074_VGAonly_DMP_64scale_PCXDUMP.png

dvwjr

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Reply 8 of 8, by digistorm

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Please use Dapplegrey's menu 'DOSBox' to 'View Config file' to see its content.

Plus, when you start the game, the config file will be written to the folder
"~/users/yourname/Library/Application Support/Dapplegrey/Unreal"

I have copied two config files, one I use for VGA demo's and generally older demo's that don't cope well with the emulated speed of a Pentium cpu, and one I use for demo's that use VESA video modes.

I don't think there are strange things going on in the config files. Additionally, I was able to reproduce the color bug on a "clean" (and brand new) iMac of a friend of mine.

Attachments

  • Filename
    DOS.conf
    File size
    1.64 KiB
    Downloads
    262 downloads
    File comment
    DOSBOX vga_only config file
    File license
    Fair use/fair dealing exception
  • Filename
    DOS1.conf
    File size
    1.62 KiB
    Downloads
    266 downloads
    File comment
    DOSBOX svga_s3 config file
    File license
    Fair use/fair dealing exception