Jump to content

  • Log In with Google      Sign In   
  • Create Account

Water Reflection and Opacity


Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.


  • You cannot reply to this topic
4 replies to this topic

#1   Members   

145
Like
0Likes
Like

Posted 25 January 2012 - 10:25 PM

Hello again!

I'm having trouble with water opacity and reflection at the same time...

I can do them apart but not at the same time.

GLvoid DrawGLScene(GLvoid){
  float look[3] = {0.0,0.0,0.0};

double eqr[] = {0.0f,0.0f, -1.0f, 0.0f};   // Plane Equation To Use For The Reflected Objects
glClearColor(0.0f,0.0f,0.0f,1.0f);

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glLoadIdentity();
add_vector(default_player->dir,look);
add_vector(default_player->cam,look);
gluLookAt(default_player->cam[0], default_player->cam[1], default_player->cam[2], look[0], look[1], look[2], 0, 0, 1);

glEnable(GL_STENCIL_TEST);	
glColorMask(0,0,0,0);  
glDisable(GL_DEPTH_TEST);	
glStencilFunc(GL_ALWAYS, 1, 1);	
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);

RenderWater();

glColorMask(1,1,1,1);	  
glEnable(GL_DEPTH_TEST);  
glStencilFunc(GL_EQUAL, 1, 1);  
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
/* DRAW */
			
glEnable(GL_CLIP_PLANE0);  
glClipPlane(GL_CLIP_PLANE0, eqr);  
glPushMatrix();	  
  glScalef(1.0f, 1.0f, -1.0f);
  glLightfv(GL_LIGHT1, GL_POSITION,default_player->light_pos);
  gl_all_textures(hash_tex, default_player,map,1);		/* terrain */
glPopMatrix();
glDisable(GL_CLIP_PLANE0);  
glDisable(GL_STENCIL_TEST);	
glLightfv(GL_LIGHT1, GL_POSITION,default_player->light_pos);

RenderSky();
RenderText();

RenderWater();   /* reflection working but no opactity */
gl_all_textures(hash_tex, default_player,map,0);	   /* terrain */
// RenderWater();  /* opacity working but no reflection */

glutSwapBuffers();
}

Posted Image

my goal is something like this:
Posted Image

#2   Members   

100
Like
0Likes
Like

Posted 26 January 2012 - 06:04 AM

Well, I'm not sure if this will work or not, but assuming that you're using alpha values for the Water (or maybe you need alpha values for the reflection?), you should be enabling blending. Usually you use it like so, you can however use it many different ways though:

glEnable(GL_BLEND); // Enables blending for OpenGL


glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); // Set the Blending function

There's a lot more OpenGL blending functions, but this might do the job, ask Google if you don't like it. Posted Image

FAQ on Transperancy:
http://www.opengl.or...ransparency.htm

Sorry if you already know this, it just doesn't seem like your enabling blending o:

#3   Members   

145
Like
0Likes
Like

Posted 26 January 2012 - 07:43 AM

void RenderWater(){
static float wx=0, wy=0;

glBindTexture(GL_TEXTURE_2D, 5);
glColor4f(0.3, 0.3, 0.3, 0.6);
glEnable(GL_BLEND);
glDisable(GL_LIGHTING);
if(default_player->lines==0){
  glBegin(GL_QUADS);
  glTexCoord2f(-map->size+wx, -map->size+wy); glVertex3f (-map->size*0.5,-map->size*0.5,0.0);
  glTexCoord2f(+map->size+wx, -map->size+wy); glVertex3f (map->size*0.5,-map->size*0.5,0.0);
  glTexCoord2f(+map->size+wx, +map->size+wy); glVertex3f (map->size*0.5,map->size*0.5,0.0);
  glTexCoord2f(-map->size+wx, +map->size+wy); glVertex3f (-map->size*0.5,map->size*0.5,0.0);
  map->water_level+=0.002;
  if(map->water_level>2*PI)
   map->water_level-=2*PI;
  glEnd();
  wx+=0.002;
  wy+=0.002;
  if(wx>8) wx-=8;
  if(wy>8) wy-=8;
}
glDisable(GL_BLEND);
glDisable(GL_LIGHTING);
}

I enabled blend in RenderWater().

#4   Moderators   

49386
Like
2Likes
Like

Posted 26 January 2012 - 07:56 AM

The technique that you're using (where you use the stencil buffer to render the regular scene and the "mirrored" scene into the same render-target) is pretty old school.
To achieve robust transparency, I would recommend rendering the "mirrored" scene into a separate render-target, and then compositing the result on top of the regular scene.

#5   Members   

805
Like
1Likes
Like

Posted 26 January 2012 - 10:09 AM

I found the following resource particularly useful, but you would have to convert to OpenGL and use shaders:

http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series4/The_water_technique.php

The explanation is pretty good though :)




Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.