Oval draw problem in Linux oolite 1.62RC3

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Wyrm
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Oval draw problem in Linux oolite 1.62RC3

Post by Wyrm »

Not sure if anyone else has this problem (and I apologise if this is known), but ovals drawn on the hud for me (or the starchart galaxy or local for that matter), have an extra straight line in them (looks like a chunk taken out of the circle). Pretty hard to miss, so it's probably a quirk somewhere else?

I'm using Fedora Core 4 / Nvidia geForce4 with Oolite 1.62R3 built from source.
I traced the problem down to the function in HeadUpDisplay.m

Code: Select all

void drawOval( double x, double y, double z, NSSize siz, int step)
changing the

Code: Select all

glBegin(GL_LINE_LOOP);
to

Code: Select all

glBegin(GL_LINE_STRIP);
and uncommenting the

Code: Select all

glVertex3f(x, y + hh, z);
makes it all better.
so the final function looks like:

Code: Select all

void drawOval( double x, double y, double z, NSSize siz, int step)
{
	int i;
	GLfloat ww = 0.5 * siz.width;
	GLfloat hh = 0.5 * siz.height;
	//glBegin(GL_LINE_LOOP);
	glBegin(GL_LINE_STRIP);
	for (i = 0; i < 360; i += step){
		glVertex3f(x + ww * sin_value[i], y + hh * sin_value[(i + 90) % 360], z);
	}
	glVertex3f(x, y + hh, z);
	glEnd();
	return;
}
note: we can get back a few cycles (not that my system is hard pressed or anything by oolite) by calculating the cos tables, so we don't have to do a + and % for every step. That's done in PlanetEntity.h/PlanetEntity.m

-Wyrm

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TGHC
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Post by TGHC »

Great first post.

Not only finds a bug but comes up with a fix for it as well.

(well he seeems to know what he is talking about, but there again how would I know)

This community is awesome.
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aegidian
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Re: Oval draw problem in Linux oolite 1.62RC3

Post by aegidian »

Wyrm wrote:Not sure if anyone else has this problem (and I apologise if this is known), but ovals drawn on the hud for me (or the starchart galaxy or local for that matter), have an extra straight line in them (looks like a chunk taken out of the circle). Pretty hard to miss, so it's probably a quirk somewhere else?

I'm using Fedora Core 4 / Nvidia geForce4 with Oolite 1.62R3 built from source.
I traced the problem down to the function in HeadUpDisplay.m
Sounds more like a problem within your particular implementation of OpenGL, although the fix you describe will work, the original code relies on the drawing GL_LINE_LOOP being properly implemented (which is IMO, a fair assumption).

I'd like to ask you to see if there is an update for your OpenGL drivers before I make any changes to Oolite's code to cope with a particular OpenGL driver problem.
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Post by winston »

Can you post a screen shot? Also, what version of the nvidia drivers are you using? (The reference ones from nvidia themselves, or is it from a yum repo such as livna or dag?)

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Rxke
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Post by Rxke »

TGHC wrote:Great first post.

Not only finds a bug but comes up with a fix for it as well.
AND an optimisation suggestion!

This community is uber-awesome!

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JensAyton
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Post by JensAyton »

Not necessarily a good optimisation, though - it would involve more memory bandwidth. A better way would be to extend the sin table by 90 entries, so you could skip the % 360, and possibly use an offset counter - that’s a 25% increase in memory load rather than 100%. If implementing this, don’t forget to profile it. ;-)

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Post by dajt »

Hi,

I'm glad someone else has seen this now ;) See http://aegidian.org/bb/viewtopic.php?t=681 for the original report.

I've been seeing it since doing the original porting work, but no-one else has ever got it.
Regards,
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Post by aegidian »

Okay, I'm convinced it's a problem with more than one OpenGL implementation.

I'm a little shattered to be coding at the moment (hungover from Burns' night - small child with chicken-pox - whisky tasting this weekend). But this fix will go in.
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Post by aegidian »

Okay changes and optimisations committed. That and a tweak to the laser graphics code are the last into v1.62. I'm releasing this weekend. Then I can get on with recoding collision detection (again).
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Post by winston »

Ah. So I should expect a busy weekend of uploading, testing, putting announcements out on Freshmeat and HappyPenguin :-)

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Post by Wyrm »

Happy to note my problem is gone. Thanks!

I'm using the Nvidia driver: NVIDIA-Linux-x86-1.0-8178
The OpenGL accel is really quite good on this card under Linux, but it's such an obvious wtf that I kinda figured it wasn't oolite. Besides, it works perfectly on my wife's mac.

-Wyrm

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