CoglDepthState

typedef struct {
} CoglDepthState;

Since 2.0

enum CoglDepthTestFunction

typedef enum {
  COGL_DEPTH_TEST_FUNCTION_NEVER    = 0x0200,
  COGL_DEPTH_TEST_FUNCTION_LESS     = 0x0201,
  COGL_DEPTH_TEST_FUNCTION_EQUAL    = 0x0202,
  COGL_DEPTH_TEST_FUNCTION_LEQUAL   = 0x0203,
  COGL_DEPTH_TEST_FUNCTION_GREATER  = 0x0204,
  COGL_DEPTH_TEST_FUNCTION_NOTEQUAL = 0x0205,
  COGL_DEPTH_TEST_FUNCTION_GEQUAL   = 0x0206,
  COGL_DEPTH_TEST_FUNCTION_ALWAYS   = 0x0207
} CoglDepthTestFunction;

When using depth testing one of these functions is used to compare the depth of an incoming fragment against the depth value currently stored in the depth buffer. The function is changed using cogl_depth_state_set_test_function().

The test is only done when depth testing is explicitly enabled. (See cogl_depth_state_set_test_enabled())

cogl_depth_state_init ()

void                cogl_depth_state_init               (CoglDepthState *state);

Initializes the members of state to their default values.

You should never pass an un initialized CoglDepthState structure to cogl_pipeline_set_depth_state().

Since 2.0

Stability Level: Unstable

cogl_depth_state_set_test_enabled ()

void                cogl_depth_state_set_test_enabled   (CoglDepthState *state,
                                                         CoglBool enable);

Enables or disables depth testing according to the value of enable.

If depth testing is enable then the CoglDepthTestFunction set using cogl_depth_state_set_test_function() us used to evaluate the depth value of incoming fragments against the corresponding value stored in the current depth buffer, and if the test passes then the fragments depth value is used to update the depth buffer. (unless you have disabled depth writing via cogl_depth_state_set_write_enabled())

By default depth testing is disabled.

NB: this won't directly affect the state of the GPU. You have to then set the state on a CoglPipeline using cogl_pipeline_set_depth_state()

Since 2.0

Stability Level: Unstable

cogl_depth_state_get_test_enabled ()

CoglBool            cogl_depth_state_get_test_enabled   (CoglDepthState *state);

Gets the current depth test enabled state as previously set by cogl_depth_state_set_test_enabled().

Since 2.0

Stability Level: Unstable

cogl_depth_state_set_test_function ()

void                cogl_depth_state_set_test_function  (CoglDepthState *state,
                                                         CoglDepthTestFunction function);

Sets the CoglDepthTestFunction used to compare the depth value of an incoming fragment against the corresponding value in the current depth buffer.

By default the depth test function is COGL_DEPTH_TEST_FUNCTION_LESS

NB: this won't directly affect the state of the GPU. You have to then set the state on a CoglPipeline using cogl_pipeline_set_depth_state()

Since 2.0

Stability Level: Unstable

cogl_depth_state_get_test_function ()

CoglDepthTestFunction cogl_depth_state_get_test_function
                                                        (CoglDepthState *state);

Gets the current depth test enable state as previously set via cogl_depth_state_set_test_enabled().

Since 2.0

Stability Level: Unstable

cogl_depth_state_set_write_enabled ()

void                cogl_depth_state_set_write_enabled  (CoglDepthState *state,
                                                         CoglBool enable);

Enables or disables depth buffer writing according to the value of enable. Normally when depth testing is enabled and the comparison between a fragment's depth value and the corresponding depth buffer value passes then the fragment's depth is written to the depth buffer unless writing is disabled here.

By default depth writing is enabled

NB: this won't directly affect the state of the GPU. You have to then set the state on a CoglPipeline using cogl_pipeline_set_depth_state()

Since 2.0

Stability Level: Unstable

cogl_depth_state_get_write_enabled ()

CoglBool            cogl_depth_state_get_write_enabled  (CoglDepthState *state);

Gets the depth writing enable state as set by the corresponding cogl_depth_state_set_write_enabled().

Since 2.0

Stability Level: Unstable

cogl_depth_state_set_range ()

void                cogl_depth_state_set_range          (CoglDepthState *state,
                                                         float near_val,
                                                         float far_val);

Sets the range to map depth values in normalized device coordinates to before writing out to a depth buffer.

After your geometry has be transformed, clipped and had perspective division applied placing it in normalized device coordinates all depth values between the near and far z clipping planes are in the range -1 to 1. Before writing any depth value to the depth buffer though the value is mapped into the range [0, 1].

With this function you can change the range which depth values are mapped too although the range must still lye within the range [0, 1].

If your driver does not support this feature (for example you are using GLES 1 drivers) then if you don't use the default range values you will get an error reported when calling cogl_pipeline_set_depth_state(). You can check ahead of time for the COGL_FEATURE_ID_DEPTH_RANGE feature with cogl_has_feature() to know if this function will succeed.

By default normalized device coordinate depth values are mapped to the full range of depth buffer values, [0, 1].

NB: this won't directly affect the state of the GPU. You have to then set the state on a CoglPipeline using cogl_pipeline_set_depth_state().

Since 2.0

Stability Level: Unstable

cogl_depth_state_get_range ()

void                cogl_depth_state_get_range          (CoglDepthState *state,
                                                         float *near_val,
                                                         float *far_val);

Gets the current range to which normalized depth values are mapped before writing to the depth buffer. This corresponds to the range set with cogl_depth_state_set_range().

Since 2.0

Stability Level: Unstable