Water Reflection and Opacity

Graphics and GPU Programming Programming

Started by HenriqueRocha January 26, 2012 04:25 AM

3 comments, last by gfxgangsta 12 years, 2 months ago

145

Author

January 26, 2012 04:25 AM

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();

}

my goal is something like this:

MiguelMartin

100

January 26, 2012 12:04 PM

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.

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:

HenriqueRocha

145

Author

January 26, 2012 01:43 PM



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().

Hodgman

52,717

January 26, 2012 01:56 PM

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.

. 22 Racing Series .

gfxgangsta

806

January 26, 2012 04:09 PM

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

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